Resource Selection Window for Sidelink Inter-UE Coordination

ABSTRACT

A first wireless device receives, from a second wireless device, a first medium access control (MAC) control element (CE) requesting for an inter-UE coordination between the first wireless device and the second wireless device, wherein the first MAC CE indicates a start time and an end time of a selection window for a resource selection procedure of the second wireless device to select resources for one or more sidelink transmissions by the second wireless device. The first wireless device selects a preferred resource set or a non-preferred resource set during the selection window. The first wireless device transmits, to the second wireless device, a second MAC CE indicating the preferred resource set or the non-preferred resource set for the second wireless device to select resources for the one or more sidelink transmissions. The first wireless device receives the one or more sidelink transmissions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/856,603, filed Jul. 1, 2022, which is a continuation of InternationalApplication No. PCT/US2021/065637, filed Dec. 30, 2021, which claims thebenefit of U.S. Provisional Application No. 63/132,300, filed Dec. 30,2020, all of which are hereby incorporated by reference in theirentireties.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of several of the various embodiments of the present disclosureare described herein with reference to the drawings.

FIG. 1A and FIG. 1B illustrate example mobile communication networks inwhich embodiments of the present disclosure may be implemented.

FIG. 2A and FIG. 2B respectively illustrate a New Radio (NR) user planeand control plane protocol stack.

FIG. 3 illustrates an example of services provided between protocollayers of the NR user plane protocol stack of FIG. 2A.

FIG. 4A illustrates an example downlink data flow through the NR userplane protocol stack of FIG. 2A.

FIG. 4B illustrates an example format of a MAC subheader in a MAC PDU.

FIG. 5A and FIG. 5B respectively illustrate a mapping between logicalchannels, transport channels, and physical channels for the downlink anduplink.

FIG. 6 is an example diagram showing RRC state transitions of a UE.

FIG. 7 illustrates an example configuration of an NR frame into whichOFDM symbols are grouped.

FIG. 8 illustrates an example configuration of a slot in the time andfrequency domain for an NR carrier.

FIG. 9 illustrates an example of bandwidth adaptation using threeconfigured BWPs for an NR carrier.

FIG. 10A illustrates three carrier aggregation configurations with twocomponent carriers.

FIG. 10B illustrates an example of how aggregated cells may beconfigured into one or more PUCCH groups.

FIG. 11A illustrates an example of an SS/PBCH block structure andlocation.

FIG. 11B illustrates an example of CSI-RSs that are mapped in the timeand frequency domains.

FIG. 12A and FIG. 12B respectively illustrate examples of three downlinkand uplink beam management procedures.

FIG. 13A, FIG. 13B, and FIG. 13C respectively illustrate a four-stepcontention-based random access procedure, a two-step contention-freerandom access procedure, and another two-step random access procedure.

FIG. 14A illustrates an example of CORESET configurations for abandwidth part.

FIG. 14B illustrates an example of a CCE-to-REG mapping for DCItransmission on a CORESET and PDCCH processing.

FIG. 15 illustrates an example of a wireless device in communicationwith a base station.

FIG. 16A, FIG. 16B, FIG. 16C, and FIG. 16D illustrate example structuresfor uplink and downlink transmission.

FIG. 17 illustrates examples of device-to-device (D2D) communication asper an aspect of an example embodiment of the present disclosure.

FIG. 18 illustrates an example of a resource pool for sidelinkoperations as per an aspect of an example embodiment of the presentdisclosure.

FIG. 19A and FIG. 19B illustrate examples of a sidelink transmission asper an aspect of an example embodiment of the present disclosure.

FIG. 20 illustrates an example of resource indication for a first TB(e.g., a first data packet) and resource reservation for a second TB(e.g., a second data packet) as per an aspect of an example embodimentof the present disclosure.

FIG. 21 illustrates an example of configuration information for sidelinkcommunication as per an aspect of an example embodiment of the presentdisclosure.

FIG. 22 illustrates an example of configuration information for sidelinkcommunication as per an aspect of an example embodiment of the presentdisclosure.

FIG. 23 illustrates an example format of a MAC subheader for sidelinkshared channel (SL-SCH) an aspect of an example embodiment of thepresent disclosure.

FIG. 24 illustrates an example time of a resource selection procedure asper an aspect of an example embodiment of the present disclosure.

FIG. 25 illustrates an example timing of a resource selection procedureas per an aspect of an example embodiment of the present disclosure.

FIG. 26 illustrates an example flowchart of a resource selectionprocedure by a wireless device for transmitting a TB via sidelink as peran aspect of an example embodiment of the present disclosure.

FIG. 27 illustrates an example diagram of the resource selectionprocedure among layers of the wireless device as per an aspect of anexample embodiment of the present disclosure.

FIG. 28 illustrates an example of inter-UE coordination for a sidelinktransmission as per an aspect of an example embodiment of the presentdisclosure.

FIG. 29 illustrates an example diagram of an inter-UE coordinationprocedure as per an aspect of an example embodiment of the presentdisclosure.

FIG. 30 illustrates examples of indicating a time by a first wirelessdevice and an estimation of the time by a second wireless device as peran aspect of an example embodiment of the present disclosure.

FIG. 31 illustrates examples of indicating a time by a first wirelessdevice and an estimation of the time by a second wireless device as peran aspect of an example embodiment of the present disclosure.

FIG. 32 illustrates an example of determining a reference time based onthe time indication in the first message and the time offset value asper an aspect of an example embodiment of the present disclosure.

DETAILED DESCRIPTION

In the present disclosure, various embodiments are presented as examplesof how the disclosed techniques may be implemented and/or how thedisclosed techniques may be practiced in environments and scenarios. Itwill be apparent to persons skilled in the relevant art that variouschanges in form and detail can be made therein without departing fromthe scope. In fact, after reading the description, it will be apparentto one skilled in the relevant art how to implement alternativeembodiments. The present embodiments should not be limited by any of thedescribed exemplary embodiments. The embodiments of the presentdisclosure will be described with reference to the accompanyingdrawings. Limitations, features, and/or elements from the disclosedexample embodiments may be combined to create further embodiments withinthe scope of the disclosure. Any figures which highlight thefunctionality and advantages, are presented for example purposes only.The disclosed architecture is sufficiently flexible and configurable,such that it may be utilized in ways other than that shown. For example,the actions listed in any flowchart may be re-ordered or only optionallyused in some embodiments.

Embodiments may be configured to operate as needed. The disclosedmechanism may be performed when certain criteria are met, for example,in a wireless device, a base station, a radio environment, a network, acombination of the above, and/or the like. Example criteria may bebased, at least in part, on for example, wireless device or network nodeconfigurations, traffic load, initial system set up, packet sizes,traffic characteristics, a combination of the above, and/or the like.When the one or more criteria are met, various example embodiments maybe applied. Therefore, it may be possible to implement exampleembodiments that selectively implement disclosed protocols.

A base station may communicate with a mix of wireless devices. Wirelessdevices and/or base stations may support multiple technologies, and/ormultiple releases of the same technology. Wireless devices may have somespecific capability(ies) depending on wireless device category and/orcapability(ies). When this disclosure refers to a base stationcommunicating with a plurality of wireless devices, this disclosure mayrefer to a subset of the total wireless devices in a coverage area. Thisdisclosure may refer to, for example, a plurality of wireless devices ofa given LTE or 5G release with a given capability and in a given sectorof the base station. The plurality of wireless devices in thisdisclosure may refer to a selected plurality of wireless devices, and/ora subset of total wireless devices in a coverage area which performaccording to disclosed methods, and/or the like. There may be aplurality of base stations or a plurality of wireless devices in acoverage area that may not comply with the disclosed methods, forexample, those wireless devices or base stations may perform based onolder releases of LTE or 5G technology.

In this disclosure, “a” and “an” and similar phrases are to beinterpreted as “at least one” and “one or more.” Similarly, any termthat ends with the suffix “(s)” is to be interpreted as “at least one”and “one or more.” In this disclosure, the term “may” is to beinterpreted as “may, for example.” In other words, the term “may” isindicative that the phrase following the term “may” is an example of oneof a multitude of suitable possibilities that may, or may not, beemployed by one or more of the various embodiments. The terms“comprises” and “consists of”, as used herein, enumerate one or morecomponents of the element being described. The term “comprises” isinterchangeable with “includes” and does not exclude unenumeratedcomponents from being included in the element being described. Bycontrast, “consists of” provides a complete enumeration of the one ormore components of the element being described. The term “based on”, asused herein, should be interpreted as “based at least in part on” ratherthan, for example, “based solely on”. The term “and/or” as used hereinrepresents any possible combination of enumerated elements. For example,“A, B, and/or C” may represent A; B; C; A and B; A and C; B and C; or A,B, and C.

If A and B are sets and every element of A is an element of B, A iscalled a subset of B. In this specification, only non-empty sets andsubsets are considered. For example, possible subsets of B={cell1,cell2} are: {cell1}, {cell2}, and {cell1, cell2}. The phrase “based on”(or equally “based at least on”) is indicative that the phrase followingthe term “based on” is an example of one of a multitude of suitablepossibilities that may, or may not, be employed to one or more of thevarious embodiments. The phrase “in response to” (or equally “inresponse at least to”) is indicative that the phrase following thephrase “in response to” is an example of one of a multitude of suitablepossibilities that may, or may not, be employed to one or more of thevarious embodiments. The phrase “depending on” (or equally “depending atleast to”) is indicative that the phrase following the phrase “dependingon” is an example of one of a multitude of suitable possibilities thatmay, or may not, be employed to one or more of the various embodiments.The phrase “employing/using” (or equally “employing/using at least”) isindicative that the phrase following the phrase “employing/using” is anexample of one of a multitude of suitable possibilities that may, or maynot, be employed to one or more of the various embodiments.

The term configured may relate to the capacity of a device whether thedevice is in an operational or non-operational state. Configured mayrefer to specific settings in a device that effect the operationalcharacteristics of the device whether the device is in an operational ornon-operational state. In other words, the hardware, software, firmware,registers, memory values, and/or the like may be “configured” within adevice, whether the device is in an operational or nonoperational state,to provide the device with specific characteristics. Terms such as “acontrol message to cause in a device” may mean that a control messagehas parameters that may be used to configure specific characteristics ormay be used to implement certain actions in the device, whether thedevice is in an operational or non-operational state.

In this disclosure, parameters (or equally called, fields, orInformation elements: IEs) may comprise one or more information objects,and an information object may comprise one or more other objects. Forexample, if parameter (IE) N comprises parameter (IE) M, and parameter(IE) M comprises parameter (IE) K, and parameter (IE) K comprisesparameter (information element) J. Then, for example, N comprises K, andN comprises J. In an example embodiment, when one or more messagescomprise a plurality of parameters, it implies that a parameter in theplurality of parameters is in at least one of the one or more messages,but does not have to be in each of the one or more messages.

Many features presented are described as being optional through the useof “may” or the use of parentheses. For the sake of brevity andlegibility, the present disclosure does not explicitly recite each andevery permutation that may be obtained by choosing from the set ofoptional features. The present disclosure is to be interpreted asexplicitly disclosing all such permutations. For example, a systemdescribed as having three optional features may be embodied in sevenways, namely with just one of the three possible features, with any twoof the three possible features or with three of the three possiblefeatures.

Many of the elements described in the disclosed embodiments may beimplemented as modules. A module is defined here as an element thatperforms a defined function and has a defined interface to otherelements. The modules described in this disclosure may be implemented inhardware, software in combination with hardware, firmware, wetware (e.g.hardware with a biological element) or a combination thereof, which maybe behaviorally equivalent. For example, modules may be implemented as asoftware routine written in a computer language configured to beexecuted by a hardware machine (such as C, C++, Fortran, Java, Basic,Matlab or the like) or a modeling/simulation program such as Simulink,Stateflow, GNU Octave, or LabVIEWMathScript. It may be possible toimplement modules using physical hardware that incorporates discrete orprogrammable analog, digital and/or quantum hardware. Examples ofprogrammable hardware comprise: computers, microcontrollers,microprocessors, application-specific integrated circuits (ASICs); fieldprogrammable gate arrays (FPGAs); and complex programmable logic devices(CPLDs). Computers, microcontrollers and microprocessors are programmedusing languages such as assembly, C, C++ or the like. FPGAs, ASICs andCPLDs are often programmed using hardware description languages (HDL)such as VHSIC hardware description language (VHDL) or Verilog thatconfigure connections between internal hardware modules with lesserfunctionality on a programmable device. The mentioned technologies areoften used in combination to achieve the result of a functional module.

FIG. 1A illustrates an example of a mobile communication network 100 inwhich embodiments of the present disclosure may be implemented. Themobile communication network 100 may be, for example, a public landmobile network (PLMN) run by a network operator. As illustrated in FIG.1A, the mobile communication network 100 includes a core network (CN)102, a radio access network (RAN) 104, and a wireless device 106.

The CN 102 may provide the wireless device 106 with an interface to oneor more data networks (DNs), such as public DNs (e.g., the Internet),private DNs, and/or intra-operator DNs. As part of the interfacefunctionality, the CN 102 may set up end-to-end connections between thewireless device 106 and the one or more DNs, authenticate the wirelessdevice 106, and provide charging functionality.

The RAN 104 may connect the CN 102 to the wireless device 106 throughradio communications over an air interface. As part of the radiocommunications, the RAN 104 may provide scheduling, radio resourcemanagement, and retransmission protocols. The communication directionfrom the RAN 104 to the wireless device 106 over the air interface isknown as the downlink and the communication direction from the wirelessdevice 106 to the RAN 104 over the air interface is known as the uplink.Downlink transmissions may be separated from uplink transmissions usingfrequency division duplexing (FDD), time-division duplexing (TDD),and/or some combination of the two duplexing techniques.

The term wireless device may be used throughout this disclosure to referto and encompass any mobile device or fixed (non-mobile) device forwhich wireless communication is needed or usable. For example, awireless device may be a telephone, smart phone, tablet, computer,laptop, sensor, meter, wearable device, Internet of Things (IoT) device,vehicle road side unit (RSU), relay node, automobile, and/or anycombination thereof. The term wireless device encompasses otherterminology, including user equipment (UE), user terminal (UT), accessterminal (AT), mobile station, handset, wireless transmit and receiveunit (WTRU), and/or wireless communication device.

The RAN 104 may include one or more base stations (not shown). The termbase station may be used throughout this disclosure to refer to andencompass a Node B (associated with UMTS and/or 3G standards), anEvolved Node B (eNB, associated with E-UTRA and/or 4G standards), aremote radio head (RRH), a baseband processing unit coupled to one ormore RRHs, a repeater node or relay node used to extend the coveragearea of a donor node, a Next Generation Evolved Node B (ng-eNB), aGeneration Node B (gNB, associated with NR and/or 5G standards), anaccess point (AP, associated with, for example, WiFi or any othersuitable wireless communication standard), and/or any combinationthereof. A base station may comprise at least one gNB Central Unit(gNB-CU) and at least one a gNB Distributed Unit (gNB-DU).

A base station included in the RAN 104 may include one or more sets ofantennas for communicating with the wireless device 106 over the airinterface. For example, one or more of the base stations may includethree sets of antennas to respectively control three cells (or sectors).The size of a cell may be determined by a range at which a receiver(e.g., a base station receiver) can successfully receive thetransmissions from a transmitter (e.g., a wireless device transmitter)operating in the cell. Together, the cells of the base stations mayprovide radio coverage to the wireless device 106 over a wide geographicarea to support wireless device mobility.

In addition to three-sector sites, other implementations of basestations are possible. For example, one or more of the base stations inthe RAN 104 may be implemented as a sectored site with more or less thanthree sectors. One or more of the base stations in the RAN 104 may beimplemented as an access point, as a baseband processing unit coupled toseveral remote radio heads (RRHs), and/or as a repeater or relay nodeused to extend the coverage area of a donor node. A baseband processingunit coupled to RRHs may be part of a centralized or cloud RANarchitecture, where the baseband processing unit may be eithercentralized in a pool of baseband processing units or virtualized. Arepeater node may amplify and rebroadcast a radio signal received from adonor node. A relay node may perform the same/similar functions as arepeater node but may decode the radio signal received from the donornode to remove noise before amplifying and rebroadcasting the radiosignal.

The RAN 104 may be deployed as a homogenous network of macrocell basestations that have similar antenna patterns and similar high-leveltransmit powers. The RAN 104 may be deployed as a heterogeneous network.In heterogeneous networks, small cell base stations may be used toprovide small coverage areas, for example, coverage areas that overlapwith the comparatively larger coverage areas provided by macrocell basestations. The small coverage areas may be provided in areas with highdata traffic (or so-called “hotspots”) or in areas with weak macrocellcoverage. Examples of small cell base stations include, in order ofdecreasing coverage area, microcell base stations, picocell basestations, and femtocell base stations or home base stations.

The Third-Generation Partnership Project (3GPP) was formed in 1998 toprovide global standardization of specifications for mobilecommunication networks similar to the mobile communication network 100in FIG. 1A. To date, 3GPP has produced specifications for threegenerations of mobile networks: a third generation (3G) network known asUniversal Mobile Telecommunications System (UMTS), a fourth generation(4G) network known as Long-Term Evolution (LTE), and a fifth generation(5G) network known as 5G System (5GS). Embodiments of the presentdisclosure are described with reference to the RAN of a 3GPP 5G network,referred to as next-generation RAN (NG-RAN). Embodiments may beapplicable to RANs of other mobile communication networks, such as theRAN 104 in FIG. 1A, the RANs of earlier 3G and 4G networks, and those offuture networks yet to be specified (e.g., a 3GPP 6G network). NG-RANimplements 5G radio access technology known as New Radio (NR) and may beprovisioned to implement 4G radio access technology or other radioaccess technologies, including non-3GPP radio access technologies.

FIG. 1B illustrates another example mobile communication network 150 inwhich embodiments of the present disclosure may be implemented. Mobilecommunication network 150 may be, for example, a PLMN run by a networkoperator. As illustrated in FIG. 1B, mobile communication network 150includes a 5G core network (5G-CN) 152, an NG-RAN 154, and UEs 156A and156B (collectively UEs 156). These components may be implemented andoperate in the same or similar manner as corresponding componentsdescribed with respect to FIG. 1A.

The 5G-CN 152 provides the UEs 156 with an interface to one or more DNs,such as public DNs (e.g., the Internet), private DNs, and/orintra-operator DNs. As part of the interface functionality, the 5G-CN152 may set up end-to-end connections between the UEs 156 and the one ormore DNs, authenticate the UEs 156, and provide charging functionality.Compared to the CN of a 3GPP 4G network, the basis of the 5G-CN 152 maybe a service-based architecture. This means that the architecture of thenodes making up the 5G-CN 152 may be defined as network functions thatoffer services via interfaces to other network functions. The networkfunctions of the 5G-CN 152 may be implemented in several ways, includingas network elements on dedicated or shared hardware, as softwareinstances running on dedicated or shared hardware, or as virtualizedfunctions instantiated on a platform (e.g., a cloud-based platform).

As illustrated in FIG. 1B, the 5G-CN 152 includes an Access and MobilityManagement Function (AMF) 158A and a User Plane Function (UPF) 158B,which are shown as one component AMF/UPF 158 in FIG. 1B for ease ofillustration. The UPF 158B may serve as a gateway between the NG-RAN 154and the one or more DNs. The UPF 158B may perform functions such aspacket routing and forwarding, packet inspection and user plane policyrule enforcement, traffic usage reporting, uplink classification tosupport routing of traffic flows to the one or more DNs, quality ofservice (QoS) handling for the user plane (e.g., packet filtering,gating, uplink/downlink rate enforcement, and uplink trafficverification), downlink packet buffering, and downlink data notificationtriggering. The UPF 158B may serve as an anchor point forintra-/inter-Radio Access Technology (RAT) mobility, an externalprotocol (or packet) data unit (PDU) session point of interconnect tothe one or more DNs, and/or a branching point to support a multi-homedPDU session. The UEs 156 may be configured to receive services through aPDU session, which is a logical connection between a UE and a DN.

The AMF 158A may perform functions such as Non-Access Stratum (NAS)signaling termination, NAS signaling security, Access Stratum (AS)security control, inter-CN node signaling for mobility between 3GPPaccess networks, idle mode UE reachability (e.g., control and executionof paging retransmission), registration area management, intra-systemand inter-system mobility support, access authentication, accessauthorization including checking of roaming rights, mobility managementcontrol (subscription and policies), network slicing support, and/orsession management function (SMF) selection. NAS may refer to thefunctionality operating between a CN and a UE, and AS may refer to thefunctionality operating between the UE and a RAN.

The 5G-CN 152 may include one or more additional network functions thatare not shown in FIG. 1B for the sake of clarity. For example, the 5G-CN152 may include one or more of a Session Management Function (SMF), anNR Repository Function (NRF), a Policy Control Function (PCF), a NetworkExposure Function (NEF), a Unified Data Management (UDM), an ApplicationFunction (AF), and/or an Authentication Server Function (AUSF).

The NG-RAN 154 may connect the 5G-CN 152 to the UEs 156 through radiocommunications over the air interface. The NG-RAN 154 may include one ormore gNBs, illustrated as gNB 160A and gNB 160B (collectively gNBs 160)and/or one or more ng-eNBs, illustrated as ng-eNB 162A and ng-eNB 162B(collectively ng-eNBs 162). The gNBs 160 and ng-eNBs 162 may be moregenerically referred to as base stations. The gNBs 160 and ng-eNBs 162may include one or more sets of antennas for communicating with the UEs156 over an air interface. For example, one or more of the gNBs 160and/or one or more of the ng-eNBs 162 may include three sets of antennasto respectively control three cells (or sectors). Together, the cells ofthe gNBs 160 and the ng-eNBs 162 may provide radio coverage to the UEs156 over a wide geographic area to support UE mobility.

As shown in FIG. 1B, the gNBs 160 and/or the ng-eNBs 162 may beconnected to the 5G-CN 152 by means of an NG interface and to other basestations by an Xn interface. The NG and Xn interfaces may be establishedusing direct physical connections and/or indirect connections over anunderlying transport network, such as an internet protocol (IP)transport network. The gNBs 160 and/or the ng-eNBs 162 may be connectedto the UEs 156 by means of a Uu interface. For example, as illustratedin FIG. 1B, gNB 160A may be connected to the UE 156A by means of a Uuinterface. The NG, Xn, and Uu interfaces are associated with a protocolstack. The protocol stacks associated with the interfaces may be used bythe network elements in FIG. 1B to exchange data and signaling messagesand may include two planes: a user plane and a control plane. The userplane may handle data of interest to a user. The control plane mayhandle signaling messages of interest to the network elements.

The gNBs 160 and/or the ng-eNBs 162 may be connected to one or moreAMF/UPF functions of the 5G-CN 152, such as the AMF/UPF 158, by means ofone or more NG interfaces. For example, the gNB 160A may be connected tothe UPF 158B of the AMF/UPF 158 by means of an NG-User plane (NG-U)interface. The NG-U interface may provide delivery (e.g., non-guaranteeddelivery) of user plane PDUs between the gNB 160A and the UPF 158B. ThegNB 160A may be connected to the AMF 158A by means of an NG-Controlplane (NG-C) interface. The NG-C interface may provide, for example, NGinterface management, UE context management, UE mobility management,transport of NAS messages, paging, PDU session management, andconfiguration transfer and/or warning message transmission.

The gNBs 160 may provide NR user plane and control plane protocolterminations towards the UEs 156 over the Uu interface. For example, thegNB 160A may provide NR user plane and control plane protocolterminations toward the UE 156A over a Uu interface associated with afirst protocol stack. The ng-eNBs 162 may provide Evolved UMTSTerrestrial Radio Access (E-UTRA) user plane and control plane protocolterminations towards the UEs 156 over a Uu interface, where E-UTRArefers to the 3GPP 4G radio-access technology. For example, the ng-eNB162B may provide E-UTRA user plane and control plane protocolterminations towards the UE 156B over a Uu interface associated with asecond protocol stack.

The 5G-CN 152 was described as being configured to handle NR and 4Gradio accesses. It will be appreciated by one of ordinary skill in theart that it may be possible for NR to connect to a 4G core network in amode known as “non-standalone operation.” In non-standalone operation, a4G core network is used to provide (or at least support) control-planefunctionality (e.g., initial access, mobility, and paging). Althoughonly one AMF/UPF 158 is shown in FIG. 1B, one gNB or ng-eNB may beconnected to multiple AMF/UPF nodes to provide redundancy and/or to loadshare across the multiple AMF/UPF nodes.

As discussed, an interface (e.g., Uu, Xn, and NG interfaces) between thenetwork elements in FIG. 1B may be associated with a protocol stack thatthe network elements use to exchange data and signaling messages. Aprotocol stack may include two planes: a user plane and a control plane.The user plane may handle data of interest to a user, and the controlplane may handle signaling messages of interest to the network elements.

FIG. 2A and FIG. 2B respectively illustrate examples of NR user planeand NR control plane protocol stacks for the Uu interface that liesbetween a UE 210 and a gNB 220. The protocol stacks illustrated in FIG.2A and FIG. 2B may be the same or similar to those used for the Uuinterface between, for example, the UE 156A and the gNB 160A shown inFIG. 1B.

FIG. 2A illustrates a NR user plane protocol stack comprising fivelayers implemented in the UE 210 and the gNB 220. At the bottom of theprotocol stack, physical layers (PHYs) 211 and 221 may provide transportservices to the higher layers of the protocol stack and may correspondto layer 1 of the Open Systems Interconnection (OSI) model. The nextfour protocols above PHYs 211 and 221 comprise media access controllayers (MACs) 212 and 222, radio link control layers (RLCs) 213 and 223,packet data convergence protocol layers (PDCPs) 214 and 224, and servicedata application protocol layers (SDAPs) 215 and 225. Together, thesefour protocols may make up layer 2, or the data link layer, of the OSImodel.

FIG. 3 illustrates an example of services provided between protocollayers of the NR user plane protocol stack. Starting from the top ofFIG. 2A and FIG. 3 , the SDAPs 215 and 225 may perform QoS flowhandling. The UE 210 may receive services through a PDU session, whichmay be a logical connection between the UE 210 and a DN. The PDU sessionmay have one or more QoS flows. A UPF of a CN (e.g., the UPF 158B) maymap IP packets to the one or more QoS flows of the PDU session based onQoS requirements (e.g., in terms of delay, data rate, and/or errorrate). The SDAPs 215 and 225 may perform mapping/de-mapping between theone or more QoS flows and one or more data radio bearers. Themapping/de-mapping between the QoS flows and the data radio bearers maybe determined by the SDAP 225 at the gNB 220. The SDAP 215 at the UE 210may be informed of the mapping between the QoS flows and the data radiobearers through reflective mapping or control signaling received fromthe gNB 220. For reflective mapping, the SDAP 225 at the gNB 220 maymark the downlink packets with a QoS flow indicator (QFI), which may beobserved by the SDAP 215 at the UE 210 to determine themapping/de-mapping between the QoS flows and the data radio bearers.

The PDCPs 214 and 224 may perform header compression/decompression toreduce the amount of data that needs to be transmitted over the airinterface, ciphering/deciphering to prevent unauthorized decoding ofdata transmitted over the air interface, and integrity protection (toensure control messages originate from intended sources. The PDCPs 214and 224 may perform retransmissions of undelivered packets, in-sequencedelivery and reordering of packets, and removal of packets received induplicate due to, for example, an intra-gNB handover. The PDCPs 214 and224 may perform packet duplication to improve the likelihood of thepacket being received and, at the receiver, remove any duplicatepackets. Packet duplication may be useful for services that require highreliability.

Although not shown in FIG. 3 , PDCPs 214 and 224 may performmapping/de-mapping between a split radio bearer and RLC channels in adual connectivity scenario. Dual connectivity is a technique that allowsa UE to connect to two cells or, more generally, two cell groups: amaster cell group (MCG) and a secondary cell group (SCG). A split beareris when a single radio bearer, such as one of the radio bearers providedby the PDCPs 214 and 224 as a service to the SDAPs 215 and 225, ishandled by cell groups in dual connectivity. The PDCPs 214 and 224 maymap/de-map the split radio bearer between RLC channels belonging to cellgroups.

The RLCs 213 and 223 may perform segmentation, retransmission throughAutomatic Repeat Request (ARQ), and removal of duplicate data unitsreceived from MACs 212 and 222, respectively. The RLCs 213 and 223 maysupport three transmission modes: transparent mode (TM); unacknowledgedmode (UM); and acknowledged mode (AM).

Based on the transmission mode an RLC is operating, the RLC may performone or more of the noted functions. The RLC configuration may be perlogical channel with no dependency on numerologies and/or TransmissionTime Interval (TTI) durations. As shown in FIG. 3 , the RLCs 213 and 223may provide RLC channels as a service to PDCPs 214 and 224,respectively.

The MACs 212 and 222 may perform multiplexing/demultiplexing of logicalchannels and/or mapping between logical channels and transport channels.The multiplexing/demultiplexing may include multiplexing/demultiplexingof data units, belonging to the one or more logical channels, into/fromTransport Blocks (TBs) delivered to/from the PHYs 211 and 221. The MAC222 may be configured to perform scheduling, scheduling informationreporting, and priority handling between UEs by means of dynamicscheduling. Scheduling may be performed in the gNB 220 (at the MAC 222)for downlink and uplink. The MACs 212 and 222 may be configured toperform error correction through Hybrid Automatic Repeat Request (HARQ)(e.g., one HARQ entity per carrier in case of Carrier Aggregation (CA)),priority handling between logical channels of the UE 210 by means oflogical channel prioritization, and/or padding. The MACs 212 and 222 maysupport one or more numerologies and/or transmission timings. In anexample, mapping restrictions in a logical channel prioritization maycontrol which numerology and/or transmission timing a logical channelmay use. As shown in FIG. 3 , the MACs 212 and 222 may provide logicalchannels as a service to the RLCs 213 and 223.

The PHYs 211 and 221 may perform mapping of transport channels tophysical channels and digital and analog signal processing functions forsending and receiving information over the air interface. These digitaland analog signal processing functions may include, for example,coding/decoding and modulation/demodulation. The PHYs 211 and 221 mayperform multi-antenna mapping. As shown in FIG. 3 , the PHYs 211 and 221may provide one or more transport channels as a service to the MACs 212and 222.

FIG. 4A illustrates an example downlink data flow through the NR userplane protocol stack. FIG. 4A illustrates a downlink data flow of threeIP packets (n, n+1, and m) through the NR user plane protocol stack togenerate two TBs at the gNB 220. An uplink data flow through the NR userplane protocol stack may be similar to the downlink data flow depictedin FIG. 4A.

The downlink data flow of FIG. 4A begins when SDAP 225 receives thethree IP packets from one or more QoS flows and maps the three packetsto radio bearers. In FIG. 4A, the SDAP 225 maps IP packets n and n+1 toa first radio bearer 402 and maps IP packet m to a second radio bearer404. An SDAP header (labeled with an “H” in FIG. 4A) is added to an IPpacket. The data unit from/to a higher protocol layer is referred to asa service data unit (SDU) of the lower protocol layer and the data unitto/from a lower protocol layer is referred to as a protocol data unit(PDU) of the higher protocol layer. As shown in FIG. 4A, the data unitfrom the SDAP 225 is an SDU of lower protocol layer PDCP 224 and is aPDU of the SDAP 225.

The remaining protocol layers in FIG. 4A may perform their associatedfunctionality (e.g., with respect to FIG. 3 ), add correspondingheaders, and forward their respective outputs to the next lower layer.For example, the PDCP 224 may perform IP-header compression andciphering and forward its output to the RLC 223. The RLC 223 mayoptionally perform segmentation (e.g., as shown for IP packet m in FIG.4A) and forward its output to the MAC 222. The MAC 222 may multiplex anumber of RLC PDUs and may attach a MAC subheader to an RLC PDU to forma transport block. In NR, the MAC subheaders may be distributed acrossthe MAC PDU, as illustrated in FIG. 4A. In LTE, the MAC subheaders maybe entirely located at the beginning of the MAC PDU. The NR MAC PDUstructure may reduce processing time and associated latency because theMAC PDU subheaders may be computed before the full MAC PDU is assembled.

FIG. 4B illustrates an example format of a MAC subheader in a MAC PDU.The MAC subheader includes: an SDU length field for indicating thelength (e.g., in bytes) of the MAC SDU to which the MAC subheadercorresponds; a logical channel identifier (LCID) field for identifyingthe logical channel from which the MAC SDU originated to aid in thedemultiplexing process; a flag (F) for indicating the size of the SDUlength field; and a reserved bit (R) field for future use.

FIG. 4B further illustrates MAC control elements (CEs) inserted into theMAC PDU by a MAC, such as MAC 223 or MAC 222. For example, FIG. 4Billustrates two MAC CEs inserted into the MAC PDU. MAC CEs may beinserted at the beginning of a MAC PDU for downlink transmissions (asshown in FIG. 4B) and at the end of a MAC PDU for uplink transmissions.MAC CEs may be used for in-band control signaling. Example MAC CEsinclude: scheduling-related MAC CEs, such as buffer status reports andpower headroom reports; activation/deactivation MAC CEs, such as thosefor activation/deactivation of PDCP duplication detection, channel stateinformation (CSI) reporting, sounding reference signal (SRS)transmission, and prior configured components; discontinuous reception(DRX) related MAC CEs; timing advance MAC CEs; and random access relatedMAC CEs. A MAC CE may be preceded by a MAC subheader with a similarformat as described for MAC SDUs and may be identified with a reservedvalue in the LCID field that indicates the type of control informationincluded in the MAC CE.

Before describing the NR control plane protocol stack, logical channels,transport channels, and physical channels are first described as well asa mapping between the channel types. One or more of the channels may beused to carry out functions associated with the NR control planeprotocol stack described later below.

FIG. 5A and FIG. 5B illustrate, for downlink and uplink respectively, amapping between logical channels, transport channels, and physicalchannels. Information is passed through channels between the RLC, theMAC, and the PHY of the NR protocol stack. A logical channel may be usedbetween the RLC and the MAC and may be classified as a control channelthat carries control and configuration information in the NR controlplane or as a traffic channel that carries data in the NR user plane. Alogical channel may be classified as a dedicated logical channel that isdedicated to a specific UE or as a common logical channel that may beused by more than one UE. A logical channel may also be defined by thetype of information it carries. The set of logical channels defined byNR include, for example:

-   -   a paging control channel (PCCH) for carrying paging messages        used to page a UE whose location is not known to the network on        a cell level;    -   a broadcast control channel (BCCH) for carrying system        information messages in the form of a master information block        (MIB) and several system information blocks (SIBs), wherein the        system information messages may be used by the UEs to obtain        information about how a cell is configured and how to operate        within the cell;    -   a common control channel (CCCH) for carrying control messages        together with random access;    -   a dedicated control channel (DCCH) for carrying control messages        to/from a specific the UE to configure the UE; and    -   a dedicated traffic channel (DTCH) for carrying user data        to/from a specific the UE.

Transport channels are used between the MAC and PHY layers and may bedefined by how the information they carry is transmitted over the airinterface. The set of transport channels defined by NR include, forexample:

-   -   a paging channel (PCH) for carrying paging messages that        originated from the PCCH;    -   a broadcast channel (BCH) for carrying the MIB from the BCCH;    -   a downlink shared channel (DL-SCH) for carrying downlink data        and signaling messages, including the SIBs from the BCCH;    -   an uplink shared channel (UL-SCH) for carrying uplink data and        signaling messages; and    -   a random access channel (RACH) for allowing a UE to contact the        network without any prior scheduling.

The PHY may use physical channels to pass information between processinglevels of the PHY. A physical channel may have an associated set oftime-frequency resources for carrying the information of one or moretransport channels. The PHY may generate control information to supportthe low-level operation of the PHY and provide the control informationto the lower levels of the PHY via physical control channels, known asL1/L2 control channels. The set of physical channels and physicalcontrol channels defined by NR include, for example:

-   -   a physical broadcast channel (PBCH) for carrying the MIB from        the BCH;    -   a physical downlink shared channel (PDSCH) for carrying downlink        data and signaling messages from the DL-SCH, as well as paging        messages from the PCH;    -   a physical downlink control channel (PDCCH) for carrying        downlink control information (DCI), which may include downlink        scheduling commands, uplink scheduling grants, and uplink power        control commands;    -   a physical uplink shared channel (PUSCH) for carrying uplink        data and signaling messages from the UL-SCH and in some        instances uplink control information (UCI) as described below;    -   a physical uplink control channel (PUCCH) for carrying UCI,        which may include HARQ acknowledgments, channel quality        indicators (CQI), pre-coding matrix indicators (PMI), rank        indicators (RI), and scheduling requests (SR); and    -   a physical random access channel (PRACH) for random access.

Similar to the physical control channels, the physical layer generatesphysical signals to support the low-level operation of the physicallayer. As shown in FIG. 5A and FIG. 5B, the physical layer signalsdefined by NR include: primary synchronization signals (PSS), secondarysynchronization signals (SSS), channel state information referencesignals (CSI-RS), demodulation reference signals (DMRS), soundingreference signals (SRS), and phase-tracking reference signals (PT-RS).These physical layer signals will be described in greater detail below.

FIG. 2B illustrates an example NR control plane protocol stack. As shownin FIG. 2B, the NR control plane protocol stack may use the same/similarfirst four protocol layers as the example NR user plane protocol stack.These four protocol layers include the PHYs 211 and 221, the MACs 212and 222, the RLCs 213 and 223, and the PDCPs 214 and 224. Instead ofhaving the SDAPs 215 and 225 at the top of the stack as in the NR userplane protocol stack, the NR control plane stack has radio resourcecontrols (RRCs) 216 and 226 and NAS protocols 217 and 237 at the top ofthe NR control plane protocol stack.

The NAS protocols 217 and 237 may provide control plane functionalitybetween the UE 210 and the AMF 230 (e.g., the AMF 158A) or, moregenerally, between the UE 210 and the CN. The NAS protocols 217 and 237may provide control plane functionality between the UE 210 and the AMF230 via signaling messages, referred to as NAS messages. There is nodirect path between the UE 210 and the AMF 230 through which the NASmessages can be transported. The NAS messages may be transported usingthe AS of the Uu and NG interfaces. NAS protocols 217 and 237 mayprovide control plane functionality such as authentication, security,connection setup, mobility management, and session management.

The RRCs 216 and 226 may provide control plane functionality between theUE 210 and the gNB 220 or, more generally, between the UE 210 and theRAN. The RRCs 216 and 226 may provide control plane functionalitybetween the UE 210 and the gNB 220 via signaling messages, referred toas RRC messages. RRC messages may be transmitted between the UE 210 andthe RAN using signaling radio bearers and the same/similar PDCP, RLC,MAC, and PHY protocol layers. The MAC may multiplex control-plane anduser-plane data into the same transport block (TB). The RRCs 216 and 226may provide control plane functionality such as: broadcast of systeminformation related to AS and NAS; paging initiated by the CN or theRAN; establishment, maintenance and release of an RRC connection betweenthe UE 210 and the RAN; security functions including key management;establishment, configuration, maintenance and release of signaling radiobearers and data radio bearers; mobility functions; QoS managementfunctions; the UE measurement reporting and control of the reporting;detection of and recovery from radio link failure (RLF); and/or NASmessage transfer. As part of establishing an RRC connection, RRCs 216and 226 may establish an RRC context, which may involve configuringparameters for communication between the UE 210 and the RAN.

FIG. 6 is an example diagram showing RRC state transitions of a UE. TheUE may be the same or similar to the wireless device 106 depicted inFIG. 1A, the UE 210 depicted in FIG. 2A and FIG. 2B, or any otherwireless device described in the present disclosure. As illustrated inFIG. 6 , a UE may be in at least one of three RRC states: RRC connected602 (e.g., RRC_CONNECTED), RRC idle 604 (e.g., RRC_IDLE), and RRCinactive 606 (e.g., RRC_INACTIVE).

In RRC connected 602, the UE has an established RRC context and may haveat least one RRC connection with a base station. The base station may besimilar to one of the one or more base stations included in the RAN 104depicted in FIG. 1A, one of the gNBs 160 or ng-eNBs 162 depicted in FIG.1B, the gNB 220 depicted in FIG. 2A and FIG. 2B, or any other basestation described in the present disclosure. The base station with whichthe UE is connected may have the RRC context for the UE. The RRCcontext, referred to as the UE context, may comprise parameters forcommunication between the UE and the base station. These parameters mayinclude, for example: one or more AS contexts; one or more radio linkconfiguration parameters; bearer configuration information (e.g.,relating to a data radio bearer, signaling radio bearer, logicalchannel, QoS flow, and/or PDU session); security information; and/orPHY, MAC, RLC, PDCP, and/or SDAP layer configuration information. Whilein RRC connected 602, mobility of the UE may be managed by the RAN(e.g., the RAN 104 or the NG-RAN 154). The UE may measure the signallevels (e.g., reference signal levels) from a serving cell andneighboring cells and report these measurements to the base stationcurrently serving the UE. The UE's serving base station may request ahandover to a cell of one of the neighboring base stations based on thereported measurements. The RRC state may transition from RRC connected602 to RRC idle 604 through a connection release procedure 608 or to RRCinactive 606 through a connection inactivation procedure 610.

In RRC idle 604, an RRC context may not be established for the UE. InRRC idle 604, the UE may not have an RRC connection with the basestation. While in RRC idle 604, the UE may be in a sleep state for themajority of the time (e.g., to conserve battery power). The UE may wakeup periodically (e.g., once in every discontinuous reception cycle) tomonitor for paging messages from the RAN. Mobility of the UE may bemanaged by the UE through a procedure known as cell reselection. The RRCstate may transition from RRC idle 604 to RRC connected 602 through aconnection establishment procedure 612, which may involve a randomaccess procedure as discussed in greater detail below.

In RRC inactive 606, the RRC context previously established ismaintained in the UE and the base station. This allows for a fasttransition to RRC connected 602 with reduced signaling overhead ascompared to the transition from RRC idle 604 to RRC connected 602. Whilein RRC inactive 606, the UE may be in a sleep state and mobility of theUE may be managed by the UE through cell reselection. The RRC state maytransition from RRC inactive 606 to RRC connected 602 through aconnection resume procedure 614 or to RRC idle 604 though a connectionrelease procedure 616 that may be the same as or similar to connectionrelease procedure 608.

An RRC state may be associated with a mobility management mechanism. InRRC idle 604 and RRC inactive 606, mobility is managed by the UE throughcell reselection. The purpose of mobility management in RRC idle 604 andRRC inactive 606 is to allow the network to be able to notify the UE ofan event via a paging message without having to broadcast the pagingmessage over the entire mobile communications network. The mobilitymanagement mechanism used in RRC idle 604 and RRC inactive 606 may allowthe network to track the UE on a cell-group level so that the pagingmessage may be broadcast over the cells of the cell group that the UEcurrently resides within instead of the entire mobile communicationnetwork. The mobility management mechanisms for RRC idle 604 and RRCinactive 606 track the UE on a cell-group level. They may do so usingdifferent granularities of grouping. For example, there may be threelevels of cell-grouping granularity: individual cells; cells within aRAN area identified by a RAN area identifier (RAI); and cells within agroup of RAN areas, referred to as a tracking area and identified by atracking area identifier (TAI).

Tracking areas may be used to track the UE at the CN level. The CN(e.g., the CN 102 or the 5G-CN 152) may provide the UE with a list ofTAIs associated with a UE registration area. If the UE moves, throughcell reselection, to a cell associated with a TAI not included in thelist of TAIs associated with the UE registration area, the UE mayperform a registration update with the CN to allow the CN to update theUE's location and provide the UE with a new the UE registration area.

RAN areas may be used to track the UE at the RAN level. For a UE in RRCinactive 606 state, the UE may be assigned a RAN notification area. ARAN notification area may comprise one or more cell identities, a listof RAIs, or a list of TAIs. In an example, a base station may belong toone or more RAN notification areas. In an example, a cell may belong toone or more RAN notification areas. If the UE moves, through cellreselection, to a cell not included in the RAN notification areaassigned to the UE, the UE may perform a notification area update withthe RAN to update the UE's RAN notification area.

A base station storing an RRC context for a UE or a last serving basestation of the UE may be referred to as an anchor base station. Ananchor base station may maintain an RRC context for the UE at leastduring a period of time that the UE stays in a RAN notification area ofthe anchor base station and/or during a period of time that the UE staysin RRC inactive 606.

A gNB, such as gNBs 160 in FIG. 1B, may be split in two parts: a centralunit (gNB-CU), and one or more distributed units (gNB-DU). A gNB-CU maybe coupled to one or more gNB-DUs using an F1 interface. The gNB-CU maycomprise the RRC, the PDCP, and the SDAP. A gNB-DU may comprise the RLC,the MAC, and the PHY.

In NR, the physical signals and physical channels (discussed withrespect to FIG. 5A and FIG. 5B) may be mapped onto orthogonal frequencydivisional multiplexing (OFDM) symbols. OFDM is a multicarriercommunication scheme that transmits data over F orthogonal subcarriers(or tones). Before transmission, the data may be mapped to a series ofcomplex symbols (e.g., M-quadrature amplitude modulation (M-QAM) orM-phase shift keying (M-PSK) symbols), referred to as source symbols,and divided into F parallel symbol streams. The F parallel symbolstreams may be treated as though they are in the frequency domain andused as inputs to an Inverse Fast Fourier Transform (IFFT) block thattransforms them into the time domain. The IFFT block may take in Fsource symbols at a time, one from each of the F parallel symbolstreams, and use each source symbol to modulate the amplitude and phaseof one of F sinusoidal basis functions that correspond to the Forthogonal subcarriers. The output of the IFFT block may be Ftime-domain samples that represent the summation of the F orthogonalsubcarriers. The F time-domain samples may form a single OFDM symbol.After some processing (e.g., addition of a cyclic prefix) andup-conversion, an OFDM symbol provided by the IFFT block may betransmitted over the air interface on a carrier frequency. The Fparallel symbol streams may be mixed using an FFT block before beingprocessed by the IFFT block. This operation produces Discrete FourierTransform (DFT)-precoded OFDM symbols and may be used by UEs in theuplink to reduce the peak to average power ratio (PAPR). Inverseprocessing may be performed on the OFDM symbol at a receiver using anFFT block to recover the data mapped to the source symbols.

FIG. 7 illustrates an example configuration of an NR frame into whichOFDM symbols are grouped. An NR frame may be identified by a systemframe number (SFN). The SFN may repeat with a period of 1024 frames. Asillustrated, one NR frame may be 10 milliseconds (ms) in duration andmay include 10 subframes that are 1 ms in duration. A subframe may bedivided into slots that include, for example, 14 OFDM symbols per slot.

The duration of a slot may depend on the numerology used for the OFDMsymbols of the slot. In NR, a flexible numerology is supported toaccommodate different cell deployments (e.g., cells with carrierfrequencies below 1 GHz up to cells with carrier frequencies in themm-wave range). A numerology may be defined in terms of subcarrierspacing and cyclic prefix duration. For a numerology in NR, subcarrierspacings may be scaled up by powers of two from a baseline subcarrierspacing of 15 kHz, and cyclic prefix durations may be scaled down bypowers of two from a baseline cyclic prefix duration of 4.7 μs. Forexample, NR defines numerologies with the following subcarrierspacing/cyclic prefix duration combinations: 15 kHz/4.7 μs; 30 kHz/2.3μs; 60 kHz/1.2 μs; 120 kHz/0.59 μs; and 240 kHz/0.29 μs.

A slot may have a fixed number of OFDM symbols (e.g., 14 OFDM symbols).A numerology with a higher subcarrier spacing has a shorter slotduration and, correspondingly, more slots per subframe. FIG. 7illustrates this numerology-dependent slot duration andslots-per-subframe transmission structure (the numerology with asubcarrier spacing of 240 kHz is not shown in FIG. 7 for ease ofillustration). A subframe in NR may be used as a numerology-independenttime reference, while a slot may be used as the unit upon which uplinkand downlink transmissions are scheduled. To support low latency,scheduling in NR may be decoupled from the slot duration and start atany OFDM symbol and last for as many symbols as needed for atransmission. These partial slot transmissions may be referred to asmini-slot or subslot transmissions.

FIG. 8 illustrates an example configuration of a slot in the time andfrequency domain for an NR carrier. The slot includes resource elements(REs) and resource blocks (RBs). An RE is the smallest physical resourcein NR. An RE spans one OFDM symbol in the time domain by one subcarrierin the frequency domain as shown in FIG. 8 . An RB spans twelveconsecutive REs in the frequency domain as shown in FIG. 8 . An NRcarrier may be limited to a width of 275 RBs or 275×12=3300 subcarriers.Such a limitation, if used, may limit the NR carrier to 50, 100, 200,and 400 MHz for subcarrier spacings of 15, 30, 60, and 120 kHz,respectively, where the 400 MHz bandwidth may be set based on a 400 MHzper carrier bandwidth limit.

FIG. 8 illustrates a single numerology being used across the entirebandwidth of the NR carrier. In other example configurations, multiplenumerologies may be supported on the same carrier.

NR may support wide carrier bandwidths (e.g., up to 400 MHz for asubcarrier spacing of 120 kHz). Not all UEs may be able to receive thefull carrier bandwidth (e.g., due to hardware limitations). Also,receiving the full carrier bandwidth may be prohibitive in terms of UEpower consumption. In an example, to reduce power consumption and/or forother purposes, a UE may adapt the size of the UE's receive bandwidthbased on the amount of traffic the UE is scheduled to receive. This isreferred to as bandwidth adaptation.

NR defines bandwidth parts (BWPs) to support UEs not capable ofreceiving the full carrier bandwidth and to support bandwidthadaptation. In an example, a BWP may be defined by a subset ofcontiguous RBs on a carrier. A UE may be configured (e.g., via RRClayer) with one or more downlink BWPs and one or more uplink BWPs perserving cell (e.g., up to four downlink BWPs and up to four uplink BWPsper serving cell). At a given time, one or more of the configured BWPsfor a serving cell may be active. These one or more BWPs may be referredto as active BWPs of the serving cell. When a serving cell is configuredwith a secondary uplink carrier, the serving cell may have one or morefirst active BWPs in the uplink carrier and one or more second activeBWPs in the secondary uplink carrier.

For unpaired spectra, a downlink BWP from a set of configured downlinkBWPs may be linked with an uplink BWP from a set of configured uplinkBWPs if a downlink BWP index of the downlink BWP and an uplink BWP indexof the uplink BWP are the same. For unpaired spectra, a UE may expectthat a center frequency for a downlink BWP is the same as a centerfrequency for an uplink BWP.

For a downlink BWP in a set of configured downlink BWPs on a primarycell (PCell), a base station may configure a UE with one or more controlresource sets (CORESETs) for at least one search space. A search spaceis a set of locations in the time and frequency domains where the UE mayfind control information. The search space may be a UE-specific searchspace or a common search space (potentially usable by a plurality ofUEs). For example, a base station may configure a UE with a commonsearch space, on a PCell or on a primary secondary cell (PSCell), in anactive downlink BWP.

For an uplink BWP in a set of configured uplink BWPs, a BS may configurea UE with one or more resource sets for one or more PUCCH transmissions.A UE may receive downlink receptions (e.g., PDCCH or PDSCH) in adownlink BWP according to a configured numerology (e.g., subcarrierspacing and cyclic prefix duration) for the downlink BWP. The UE maytransmit uplink transmissions (e.g., PUCCH or PUSCH) in an uplink BWPaccording to a configured numerology (e.g., subcarrier spacing andcyclic prefix length for the uplink BWP).

One or more BWP indicator fields may be provided in Downlink ControlInformation (DCI). A value of a BWP indicator field may indicate whichBWP in a set of configured BWPs is an active downlink BWP for one ormore downlink receptions. The value of the one or more BWP indicatorfields may indicate an active uplink BWP for one or more uplinktransmissions.

A base station may semi-statically configure a UE with a defaultdownlink BWP within a set of configured downlink BWPs associated with aPCell. If the base station does not provide the default downlink BWP tothe UE, the default downlink BWP may be an initial active downlink BWP.The UE may determine which BWP is the initial active downlink BWP basedon a CORESET configuration obtained using the PBCH.

A base station may configure a UE with a BWP inactivity timer value fora PCell. The UE may start or restart a BWP inactivity timer at anyappropriate time. For example, the UE may start or restart the BWPinactivity timer (a) when the UE detects a DCI indicating an activedownlink BWP other than a default downlink BWP for a paired spectraoperation; or (b) when a UE detects a DCI indicating an active downlinkBWP or active uplink BWP other than a default downlink BWP or uplink BWPfor an unpaired spectra operation. If the UE does not detect DCI duringan interval of time (e.g., 1 ms or 0.5 ms), the UE may run the BWPinactivity timer toward expiration (for example, increment from zero tothe BWP inactivity timer value, or decrement from the BWP inactivitytimer value to zero). When the BWP inactivity timer expires, the UE mayswitch from the active downlink BWP to the default downlink BWP.

In an example, a base station may semi-statically configure a UE withone or more BWPs. A UE may switch an active BWP from a first BWP to asecond BWP in response to receiving a DCI indicating the second BWP asan active BWP and/or in response to an expiry of the BWP inactivitytimer (e.g., if the second BWP is the default BWP).

Downlink and uplink BWP switching (where BWP switching refers toswitching from a currently active BWP to a not currently active BWP) maybe performed independently in paired spectra. In unpaired spectra,downlink and uplink BWP switching may be performed simultaneously.Switching between configured BWPs may occur based on RRC signaling, DCI,expiration of a BWP inactivity timer, and/or an initiation of randomaccess.

FIG. 9 illustrates an example of bandwidth adaptation using threeconfigured BWPs for an NR carrier. A UE configured with the three BWPsmay switch from one BWP to another BWP at a switching point. In theexample illustrated in FIG. 9 , the BWPs include: a BWP 902 with abandwidth of 40 MHz and a subcarrier spacing of 15 kHz; a BWP 904 with abandwidth of 10 MHz and a subcarrier spacing of 15 kHz; and a BWP 906with a bandwidth of 20 MHz and a subcarrier spacing of 60 kHz. The BWP902 may be an initial active BWP, and the BWP 904 may be a default BWP.The UE may switch between BWPs at switching points. In the example ofFIG. 9 , the UE may switch from the BWP 902 to the BWP 904 at aswitching point 908. The switching at the switching point 908 may occurfor any suitable reason, for example, in response to an expiry of a BWPinactivity timer (indicating switching to the default BWP) and/or inresponse to receiving a DCI indicating BWP 904 as the active BWP. The UEmay switch at a switching point 910 from active BWP 904 to BWP 906 inresponse receiving a DCI indicating BWP 906 as the active BWP. The UEmay switch at a switching point 912 from active BWP 906 to BWP 904 inresponse to an expiry of a BWP inactivity timer and/or in responsereceiving a DCI indicating BWP 904 as the active BWP. The UE may switchat a switching point 914 from active BWP 904 to BWP 902 in responsereceiving a DCI indicating BWP 902 as the active BWP.

If a UE is configured for a secondary cell with a default downlink BWPin a set of configured downlink BWPs and a timer value, UE proceduresfor switching BWPs on a secondary cell may be the same/similar as thoseon a primary cell. For example, the UE may use the timer value and thedefault downlink BWP for the secondary cell in the same/similar manneras the UE would use these values for a primary cell.

To provide for greater data rates, two or more carriers can beaggregated and simultaneously transmitted to/from the same UE usingcarrier aggregation (CA). The aggregated carriers in CA may be referredto as component carriers (CCs). When CA is used, there are a number ofserving cells for the UE, one for a CC. The CCs may have threeconfigurations in the frequency domain.

FIG. 10A illustrates the three CA configurations with two CCs. In theintraband, contiguous configuration 1002, the two CCs are aggregated inthe same frequency band (frequency band A) and are located directlyadjacent to each other within the frequency band. In the intraband,non-contiguous configuration 1004, the two CCs are aggregated in thesame frequency band (frequency band A) and are separated in thefrequency band by a gap. In the interband configuration 1006, the twoCCs are located in frequency bands (frequency band A and frequency bandB).

In an example, up to 32 CCs may be aggregated. The aggregated CCs mayhave the same or different bandwidths, subcarrier spacing, and/orduplexing schemes (TDD or FDD). A serving cell for a UE using CA mayhave a downlink CC. For FDD, one or more uplink CCs may be optionallyconfigured for a serving cell. The ability to aggregate more downlinkcarriers than uplink carriers may be useful, for example, when the UEhas more data traffic in the downlink than in the uplink.

When CA is used, one of the aggregated cells for a UE may be referred toas a primary cell (PCell). The PCell may be the serving cell that the UEinitially connects to at RRC connection establishment, reestablishment,and/or handover. The PCell may provide the UE with NAS mobilityinformation and the security input. UEs may have different PCells. Inthe downlink, the carrier corresponding to the PCell may be referred toas the downlink primary CC (DL PCC). In the uplink, the carriercorresponding to the PCell may be referred to as the uplink primary CC(UL PCC). The other aggregated cells for the UE may be referred to assecondary cells (SCells). In an example, the SCells may be configuredafter the PCell is configured for the UE. For example, an SCell may beconfigured through an RRC Connection Reconfiguration procedure. In thedownlink, the carrier corresponding to an SCell may be referred to as adownlink secondary CC (DL SCC). In the uplink, the carrier correspondingto the SCell may be referred to as the uplink secondary CC (UL SCC).

Configured SCells for a UE may be activated and deactivated based on,for example, traffic and channel conditions. Deactivation of an SCellmay mean that PDCCH and PDSCH reception on the SCell is stopped andPUSCH, SRS, and CQI transmissions on the SCell are stopped. ConfiguredSCells may be activated and deactivated using a MAC CE with respect toFIG. 4B. For example, a MAC CE may use a bitmap (e.g., one bit perSCell) to indicate which SCells (e.g., in a subset of configured SCells)for the UE are activated or deactivated. Configured SCells may bedeactivated in response to an expiration of an SCell deactivation timer(e.g., one SCell deactivation timer per SCell).

Downlink control information, such as scheduling assignments andscheduling grants, for a cell may be transmitted on the cellcorresponding to the assignments and grants, which is known asself-scheduling. The DCI for the cell may be transmitted on anothercell, which is known as cross-carrier scheduling. Uplink controlinformation (e.g., HARQ acknowledgments and channel state feedback, suchas CQI, PMI, and/or RI) for aggregated cells may be transmitted on thePUCCH of the PCell. For a larger number of aggregated downlink CCs, thePUCCH of the PCell may become overloaded. Cells may be divided intomultiple PUCCH groups.

FIG. 10B illustrates an example of how aggregated cells may beconfigured into one or more PUCCH groups. A PUCCH group 1010 and a PUCCHgroup 1050 may include one or more downlink CCs, respectively. In theexample of FIG. 10B, the PUCCH group 1010 includes three downlink CCs: aPCell 1011, an SCell 1012, and an SCell 1013. The PUCCH group 1050includes three downlink CCs in the present example: a PCell 1051, anSCell 1052, and an SCell 1053. One or more uplink CCs may be configuredas a PCell 1021, an SCell 1022, and an SCell 1023. One or more otheruplink CCs may be configured as a primary Scell (PSCell) 1061, an SCell1062, and an SCell 1063. Uplink control information (UCI) related to thedownlink CCs of the PUCCH group 1010, shown as UCI 1031, UCI 1032, andUCI 1033, may be transmitted in the uplink of the PCell 1021. Uplinkcontrol information (UCI) related to the downlink CCs of the PUCCH group1050, shown as UCI 1071, UCI 1072, and UCI 1073, may be transmitted inthe uplink of the PSCell 1061. In an example, if the aggregated cellsdepicted in FIG. 10B were not divided into the PUCCH group 1010 and thePUCCH group 1050, a single uplink PCell to transmit UCI relating to thedownlink CCs, and the PCell may become overloaded. By dividingtransmissions of UCI between the PCell 1021 and the PSCell 1061,overloading may be prevented.

A cell, comprising a downlink carrier and optionally an uplink carrier,may be assigned with a physical cell ID and a cell index. The physicalcell ID or the cell index may identify a downlink carrier and/or anuplink carrier of the cell, for example, depending on the context inwhich the physical cell ID is used. A physical cell ID may be determinedusing a synchronization signal transmitted on a downlink componentcarrier. A cell index may be determined using RRC messages. In thedisclosure, a physical cell ID may be referred to as a carrier ID, and acell index may be referred to as a carrier index. For example, when thedisclosure refers to a first physical cell ID for a first downlinkcarrier, the disclosure may mean the first physical cell ID is for acell comprising the first downlink carrier. The same/similar concept mayapply to, for example, a carrier activation. When the disclosureindicates that a first carrier is activated, the specification may meanthat a cell comprising the first carrier is activated.

In CA, a multi-carrier nature of a PHY may be exposed to a MAC. In anexample, a HARQ entity may operate on a serving cell. A transport blockmay be generated per assignment/grant per serving cell. A transportblock and potential HARQ retransmissions of the transport block may bemapped to a serving cell.

In the downlink, a base station may transmit (e.g., unicast, multicast,and/or broadcast) one or more Reference Signals (RSs) to a UE (e.g.,PSS, SSS, CSI-RS, DMRS, and/or PT-RS, as shown in FIG. 5A). In theuplink, the UE may transmit one or more RSs to the base station (e.g.,DMRS, PT-RS, and/or SRS, as shown in FIG. 5B). The PSS and the SSS maybe transmitted by the base station and used by the UE to synchronize theUE to the base station. The PSS and the SSS may be provided in asynchronization signal (SS)/physical broadcast channel (PBCH) block thatincludes the PSS, the SSS, and the PBCH. The base station mayperiodically transmit a burst of SS/PBCH blocks.

FIG. 11A illustrates an example of an SS/PBCH block's structure andlocation. A burst of SS/PBCH blocks may include one or more SS/PBCHblocks (e.g., 4 SS/PBCH blocks, as shown in FIG. 11A). Bursts may betransmitted periodically (e.g., every 2 frames or 20 ms). A burst may berestricted to a half-frame (e.g., a first half-frame having a durationof 5 ms). It will be understood that FIG. 11A is an example, and thatthese parameters (number of SS/PBCH blocks per burst, periodicity ofbursts, position of burst within the frame) may be configured based on,for example: a carrier frequency of a cell in which the SS/PBCH block istransmitted; a numerology or subcarrier spacing of the cell; aconfiguration by the network (e.g., using RRC signaling); or any othersuitable factor. In an example, the UE may assume a subcarrier spacingfor the SS/PBCH block based on the carrier frequency being monitored,unless the radio network configured the UE to assume a differentsubcarrier spacing.

The SS/PBCH block may span one or more OFDM symbols in the time domain(e.g., 4 OFDM symbols, as shown in the example of FIG. 11A) and may spanone or more subcarriers in the frequency domain (e.g., 240 contiguoussubcarriers). The PSS, the SSS, and the PBCH may have a common centerfrequency. The PSS may be transmitted first and may span, for example, 1OFDM symbol and 127 subcarriers. The SSS may be transmitted after thePSS (e.g., two symbols later) and may span 1 OFDM symbol and 127subcarriers. The PBCH may be transmitted after the PSS (e.g., across thenext 3 OFDM symbols) and may span 240 subcarriers.

The location of the SS/PBCH block in the time and frequency domains maynot be known to the UE (e.g., if the UE is searching for the cell). Tofind and select the cell, the UE may monitor a carrier for the PSS. Forexample, the UE may monitor a frequency location within the carrier. Ifthe PSS is not found after a certain duration (e.g., 20 ms), the UE maysearch for the PSS at a different frequency location within the carrier,as indicated by a synchronization raster. If the PSS is found at alocation in the time and frequency domains, the UE may determine, basedon a known structure of the SS/PBCH block, the locations of the SSS andthe PBCH, respectively. The SS/PBCH block may be a cell-defining SSblock (CD-SSB). In an example, a primary cell may be associated with aCD-SSB. The CD-SSB may be located on a synchronization raster. In anexample, a cell selection/search and/or reselection may be based on theCD-SSB.

The SS/PBCH block may be used by the UE to determine one or moreparameters of the cell. For example, the UE may determine a physicalcell identifier (PCI) of the cell based on the sequences of the PSS andthe SSS, respectively. The UE may determine a location of a frameboundary of the cell based on the location of the SS/PBCH block. Forexample, the SS/PBCH block may indicate that it has been transmitted inaccordance with a transmission pattern, wherein a SS/PBCH block in thetransmission pattern is a known distance from the frame boundary.

The PBCH may use a QPSK modulation and may use forward error correction(FEC). The FEC may use polar coding. One or more symbols spanned by thePBCH may carry one or more DMRSs for demodulation of the PBCH. The PBCHmay include an indication of a current system frame number (SFN) of thecell and/or a SS/PBCH block timing index. These parameters mayfacilitate time synchronization of the UE to the base station. The PBCHmay include a master information block (MIB) used to provide the UE withone or more parameters. The MIB may be used by the UE to locateremaining minimum system information (RMSI) associated with the cell.The RMSI may include a System Information Block Type 1 (SIB1). The SIB1may contain information needed by the UE to access the cell. The UE mayuse one or more parameters of the MIB to monitor PDCCH, which may beused to schedule PDSCH. The PDSCH may include the SIB1. The SIB1 may bedecoded using parameters provided in the MIB. The PBCH may indicate anabsence of SIB1. Based on the PBCH indicating the absence of SIB1, theUE may be pointed to a frequency. The UE may search for an SS/PBCH blockat the frequency to which the UE is pointed.

The UE may assume that one or more SS/PBCH blocks transmitted with asame SS/PBCH block index are quasi co-located (QCLed) (e.g., having thesame/similar Doppler spread, Doppler shift, average gain, average delay,and/or spatial Rx parameters). The UE may not assume QCL for SS/PBCHblock transmissions having different SS/PBCH block indices.

SS/PBCH blocks (e.g., those within a half-frame) may be transmitted inspatial directions (e.g., using different beams that span a coveragearea of the cell). In an example, a first SS/PBCH block may betransmitted in a first spatial direction using a first beam, and asecond SS/PBCH block may be transmitted in a second spatial directionusing a second beam.

In an example, within a frequency span of a carrier, a base station maytransmit a plurality of SS/PBCH blocks. In an example, a first PCI of afirst SS/PBCH block of the plurality of SS/PBCH blocks may be differentfrom a second PCI of a second SS/PBCH block of the plurality of SS/PBCHblocks. The PCIs of SS/PBCH blocks transmitted in different frequencylocations may be different or the same.

The CSI-RS may be transmitted by the base station and used by the UE toacquire channel state information (CSI). The base station may configurethe UE with one or more CSI-RSs for channel estimation or any othersuitable purpose. The base station may configure a UE with one or moreof the same/similar CSI-RSs. The UE may measure the one or more CSI-RSs.The UE may estimate a downlink channel state and/or generate a CSIreport based on the measuring of the one or more downlink CSI-RSs. TheUE may provide the CSI report to the base station. The base station mayuse feedback provided by the UE (e.g., the estimated downlink channelstate) to perform link adaptation.

The base station may semi-statically configure the UE with one or moreCSI-RS resource sets. A CSI-RS resource may be associated with alocation in the time and frequency domains and a periodicity. The basestation may selectively activate and/or deactivate a CSI-RS resource.The base station may indicate to the UE that a CSI-RS resource in theCSI-RS resource set is activated and/or deactivated.

The base station may configure the UE to report CSI measurements. Thebase station may configure the UE to provide CSI reports periodically,aperiodically, or semi-persistently. For periodic CSI reporting, the UEmay be configured with a timing and/or periodicity of a plurality of CSIreports. For aperiodic CSI reporting, the base station may request a CSIreport. For example, the base station may command the UE to measure aconfigured CSI-RS resource and provide a CSI report relating to themeasurements. For semi-persistent CSI reporting, the base station mayconfigure the UE to transmit periodically, and selectively activate ordeactivate the periodic reporting. The base station may configure the UEwith a CSI-RS resource set and CSI reports using RRC signaling.

The CSI-RS configuration may comprise one or more parameters indicating,for example, up to 32 antenna ports. The UE may be configured to employthe same OFDM symbols for a downlink CSI-RS and a control resource set(CORESET) when the downlink CSI-RS and CORESET are spatially QCLed andresource elements associated with the downlink CSI-RS are outside of thephysical resource blocks (PRBs) configured for the CORESET. The UE maybe configured to employ the same OFDM symbols for downlink CSI-RS andSS/PBCH blocks when the downlink CSI-RS and SS/PBCH blocks are spatiallyQCLed and resource elements associated with the downlink CSI-RS areoutside of PRBs configured for the SS/PBCH blocks.

Downlink DMRSs may be transmitted by a base station and used by a UE forchannel estimation. For example, the downlink DMRS may be used forcoherent demodulation of one or more downlink physical channels (e.g.,PDSCH). An NR network may support one or more variable and/orconfigurable DMRS patterns for data demodulation. At least one downlinkDMRS configuration may support a front-loaded DMRS pattern. Afront-loaded DMRS may be mapped over one or more OFDM symbols (e.g., oneor two adjacent OFDM symbols). A base station may semi-staticallyconfigure the UE with a number (e.g. a maximum number) of front-loadedDMRS symbols for PDSCH. A DMRS configuration may support one or moreDMRS ports. For example, for single user-MIMO, a DMRS configuration maysupport up to eight orthogonal downlink DMRS ports per UE. Formultiuser-MIMO, a DMRS configuration may support up to 4 orthogonaldownlink DMRS ports per UE. A radio network may support (e.g., at leastfor CP-OFDM) a common DMRS structure for downlink and uplink, wherein aDMRS location, a DMRS pattern, and/or a scrambling sequence may be thesame or different. The base station may transmit a downlink DMRS and acorresponding PDSCH using the same precoding matrix. The UE may use theone or more downlink DMRSs for coherent demodulation/channel estimationof the PDSCH.

In an example, a transmitter (e.g., a base station) may use a precodermatrices for a part of a transmission bandwidth. For example, thetransmitter may use a first precoder matrix for a first bandwidth and asecond precoder matrix for a second bandwidth. The first precoder matrixand the second precoder matrix may be different based on the firstbandwidth being different from the second bandwidth. The UE may assumethat a same precoding matrix is used across a set of PRBs. The set ofPRBs may be denoted as a precoding resource block group (PRG).

A PDSCH may comprise one or more layers. The UE may assume that at leastone symbol with DMRS is present on a layer of the one or more layers ofthe PDSCH. A higher layer may configure up to 3 DMRSs for the PDSCH.

Downlink PT-RS may be transmitted by a base station and used by a UE forphase-noise compensation. Whether a downlink PT-RS is present or not maydepend on an RRC configuration. The presence and/or pattern of thedownlink PT-RS may be configured on a UE-specific basis using acombination of RRC signaling and/or an association with one or moreparameters employed for other purposes (e.g., modulation and codingscheme (MCS)), which may be indicated by DCI. When configured, a dynamicpresence of a downlink PT-RS may be associated with one or more DCIparameters comprising at least MCS. An NR network may support aplurality of PT-RS densities defined in the time and/or frequencydomains. When present, a frequency domain density may be associated withat least one configuration of a scheduled bandwidth. The UE may assume asame precoding for a DMRS port and a PT-RS port. A number of PT-RS portsmay be fewer than a number of DMRS ports in a scheduled resource.Downlink PT-RS may be confined in the scheduled time/frequency durationfor the UE. Downlink PT-RS may be transmitted on symbols to facilitatephase tracking at the receiver.

The UE may transmit an uplink DMRS to a base station for channelestimation. For example, the base station may use the uplink DMRS forcoherent demodulation of one or more uplink physical channels. Forexample, the UE may transmit an uplink DMRS with a PUSCH and/or a PUCCH.The uplink DM-RS may span a range of frequencies that is similar to arange of frequencies associated with the corresponding physical channel.The base station may configure the UE with one or more uplink DMRSconfigurations. At least one DMRS configuration may support afront-loaded DMRS pattern. The front-loaded DMRS may be mapped over oneor more OFDM symbols (e.g., one or two adjacent OFDM symbols). One ormore uplink DMRSs may be configured to transmit at one or more symbolsof a PUSCH and/or a PUCCH. The base station may semi-staticallyconfigure the UE with a number (e.g. maximum number) of front-loadedDMRS symbols for the PUSCH and/or the PUCCH, which the UE may use toschedule a single-symbol DMRS and/or a double-symbol DMRS. An NR networkmay support (e.g., for cyclic prefix orthogonal frequency divisionmultiplexing (CP-OFDM)) a common DMRS structure for downlink and uplink,wherein a DMRS location, a DMRS pattern, and/or a scrambling sequencefor the DMRS may be the same or different.

A PUSCH may comprise one or more layers, and the UE may transmit atleast one symbol with DMRS present on a layer of the one or more layersof the PUSCH. In an example, a higher layer may configure up to threeDMRSs for the PUSCH.

Uplink PT-RS (which may be used by a base station for phase trackingand/or phase-noise compensation) may or may not be present depending onan RRC configuration of the UE. The presence and/or pattern of uplinkPT-RS may be configured on a UE-specific basis by a combination of RRCsignaling and/or one or more parameters employed for other purposes(e.g., Modulation and Coding Scheme (MCS)), which may be indicated byDCI. When configured, a dynamic presence of uplink PT-RS may beassociated with one or more DCI parameters comprising at least MCS. Aradio network may support a plurality of uplink PT-RS densities definedin time/frequency domain. When present, a frequency domain density maybe associated with at least one configuration of a scheduled bandwidth.The UE may assume a same precoding for a DMRS port and a PT-RS port. Anumber of PT-RS ports may be fewer than a number of DMRS ports in ascheduled resource. For example, uplink PT-RS may be confined in thescheduled time/frequency duration for the UE.

SRS may be transmitted by a UE to a base station for channel stateestimation to support uplink channel dependent scheduling and/or linkadaptation. SRS transmitted by the UE may allow a base station toestimate an uplink channel state at one or more frequencies. A schedulerat the base station may employ the estimated uplink channel state toassign one or more resource blocks for an uplink PUSCH transmission fromthe UE. The base station may semi-statically configure the UE with oneor more SRS resource sets. For an SRS resource set, the base station mayconfigure the UE with one or more SRS resources. An SRS resource setapplicability may be configured by a higher layer (e.g., RRC) parameter.For example, when a higher layer parameter indicates beam management, anSRS resource in a SRS resource set of the one or more SRS resource sets(e.g., with the same/similar time domain behavior, periodic, aperiodic,and/or the like) may be transmitted at a time instant (e.g.,simultaneously). The UE may transmit one or more SRS resources in SRSresource sets. An NR network may support aperiodic, periodic and/orsemi-persistent SRS transmissions. The UE may transmit SRS resourcesbased on one or more trigger types, wherein the one or more triggertypes may comprise higher layer signaling (e.g., RRC) and/or one or moreDCI formats. In an example, at least one DCI format may be employed forthe UE to select at least one of one or more configured SRS resourcesets. An SRS trigger type 0 may refer to an SRS triggered based on ahigher layer signaling. An SRS trigger type 1 may refer to an SRStriggered based on one or more DCI formats. In an example, when PUSCHand SRS are transmitted in a same slot, the UE may be configured totransmit SRS after a transmission of a PUSCH and a corresponding uplinkDMRS.

The base station may semi-statically configure the UE with one or moreSRS configuration parameters indicating at least one of following: a SRSresource configuration identifier; a number of SRS ports; time domainbehavior of an SRS resource configuration (e.g., an indication ofperiodic, semi-persistent, or aperiodic SRS); slot, mini-slot, and/orsubframe level periodicity; offset for a periodic and/or an aperiodicSRS resource; a number of OFDM symbols in an SRS resource; a startingOFDM symbol of an SRS resource; an SRS bandwidth; a frequency hoppingbandwidth; a cyclic shift; and/or an SRS sequence ID.

An antenna port is defined such that the channel over which a symbol onthe antenna port is conveyed can be inferred from the channel over whichanother symbol on the same antenna port is conveyed. If a first symboland a second symbol are transmitted on the same antenna port, thereceiver may infer the channel (e.g., fading gain, multipath delay,and/or the like) for conveying the second symbol on the antenna port,from the channel for conveying the first symbol on the antenna port. Afirst antenna port and a second antenna port may be referred to as quasico-located (QCLed) if one or more large-scale properties of the channelover which a first symbol on the first antenna port is conveyed may beinferred from the channel over which a second symbol on a second antennaport is conveyed. The one or more large-scale properties may comprise atleast one of: a delay spread; a Doppler spread; a Doppler shift; anaverage gain; an average delay; and/or spatial Receiving (Rx)parameters.

Channels that use beamforming require beam management. Beam managementmay comprise beam measurement, beam selection, and beam indication. Abeam may be associated with one or more reference signals. For example,a beam may be identified by one or more beamformed reference signals.The UE may perform downlink beam measurement based on downlink referencesignals (e.g., a channel state information reference signal (CSI-RS))and generate a beam measurement report. The UE may perform the downlinkbeam measurement procedure after an RRC connection is set up with a basestation.

FIG. 11B illustrates an example of channel state information referencesignals (CSI-RSs) that are mapped in the time and frequency domains. Asquare shown in FIG. 11B may span a resource block (RB) within abandwidth of a cell. A base station may transmit one or more RRCmessages comprising CSI-RS resource configuration parameters indicatingone or more CSI-RSs. One or more of the following parameters may beconfigured by higher layer signaling (e.g., RRC and/or MAC signaling)for a CSI-RS resource configuration: a CSI-RS resource configurationidentity, a number of CSI-RS ports, a CSI-RS configuration (e.g., symboland resource element (RE) locations in a subframe), a CSI-RS subframeconfiguration (e.g., subframe location, offset, and periodicity in aradio frame), a CSI-RS power parameter, a CSI-RS sequence parameter, acode division multiplexing (CDM) type parameter, a frequency density, atransmission comb, quasi co-location (QCL) parameters (e.g.,QCL-scramblingidentity, crs-portscount, mbsfn-subframeconfiglist,csi-rs-configZPid, qcl-csi-rs-configNZPid), and/or other radio resourceparameters.

The three beams illustrated in FIG. 11B may be configured for a UE in aUE-specific configuration. Three beams are illustrated in FIG. 11B (beam#1, beam #2, and beam #3), more or fewer beams may be configured. Beam#1 may be allocated with CSI-RS 1101 that may be transmitted in one ormore subcarriers in an RB of a first symbol. Beam #2 may be allocatedwith CSI-RS 1102 that may be transmitted in one or more subcarriers inan RB of a second symbol. Beam #3 may be allocated with CSI-RS 1103 thatmay be transmitted in one or more subcarriers in an RB of a thirdsymbol. By using frequency division multiplexing (FDM), a base stationmay use other subcarriers in a same RB (for example, those that are notused to transmit CSI-RS 1101) to transmit another CSI-RS associated witha beam for another UE. By using time domain multiplexing (TDM), beamsused for the UE may be configured such that beams for the UE use symbolsfrom beams of other UEs.

CSI-RSs such as those illustrated in FIG. 11B (e.g., CSI-RS 1101, 1102,1103) may be transmitted by the base station and used by the UE for oneor more measurements. For example, the UE may measure a reference signalreceived power (RSRP) of configured CSI-RS resources. The base stationmay configure the UE with a reporting configuration and the UE mayreport the RSRP measurements to a network (for example, via one or morebase stations) based on the reporting configuration. In an example, thebase station may determine, based on the reported measurement results,one or more transmission configuration indication (TCI) statescomprising a number of reference signals. In an example, the basestation may indicate one or more TCI states to the UE (e.g., via RRCsignaling, a MAC CE, and/or a DCI). The UE may receive a downlinktransmission with a receive (Rx) beam determined based on the one ormore TCI states. In an example, the UE may or may not have a capabilityof beam correspondence. If the UE has the capability of beamcorrespondence, the UE may determine a spatial domain filter of atransmit (Tx) beam based on a spatial domain filter of the correspondingRx beam. If the UE does not have the capability of beam correspondence,the UE may perform an uplink beam selection procedure to determine thespatial domain filter of the Tx beam. The UE may perform the uplink beamselection procedure based on one or more sounding reference signal (SRS)resources configured to the UE by the base station. The base station mayselect and indicate uplink beams for the UE based on measurements of theone or more SRS resources transmitted by the UE.

In a beam management procedure, a UE may assess (e.g., measure) achannel quality of one or more beam pair links, a beam pair linkcomprising a transmitting beam transmitted by a base station and areceiving beam received by the UE. Based on the assessment, the UE maytransmit a beam measurement report indicating one or more beam pairquality parameters comprising, e.g., one or more beam identifications(e.g., a beam index, a reference signal index, or the like), RSRP, aprecoding matrix indicator (PMI), a channel quality indicator (CQI),and/or a rank indicator (RI).

FIG. 12A illustrates examples of three downlink beam managementprocedures: P1, P2, and P3. Procedure P1 may enable a UE measurement ontransmit (Tx) beams of a transmission reception point (TRP) (or multipleTRPs), e.g., to support a selection of one or more base station Tx beamsand/or UE Rx beams (shown as ovals in the top row and bottom row,respectively, of P1). Beamforming at a TRP may comprise a Tx beam sweepfor a set of beams (shown, in the top rows of P1 and P2, as ovalsrotated in a counter-clockwise direction indicated by the dashed arrow).Beamforming at a UE may comprise an Rx beam sweep for a set of beams(shown, in the bottom rows of P1 and P3, as ovals rotated in a clockwisedirection indicated by the dashed arrow). Procedure P2 may be used toenable a UE measurement on Tx beams of a TRP (shown, in the top row ofP2, as ovals rotated in a counter-clockwise direction indicated by thedashed arrow). The UE and/or the base station may perform procedure P2using a smaller set of beams than is used in procedure P1, or usingnarrower beams than the beams used in procedure P1. This may be referredto as beam refinement. The UE may perform procedure P3 for Rx beamdetermination by using the same Tx beam at the base station and sweepingan Rx beam at the UE.

FIG. 12B illustrates examples of three uplink beam managementprocedures: U1, U2, and U3. Procedure U1 may be used to enable a basestation to perform a measurement on Tx beams of a UE, e.g., to support aselection of one or more UE Tx beams and/or base station Rx beams (shownas ovals in the top row and bottom row, respectively, of U1).Beamforming at the UE may include, e.g., a Tx beam sweep from a set ofbeams (shown in the bottom rows of U1 and U3 as ovals rotated in aclockwise direction indicated by the dashed arrow). Beamforming at thebase station may include, e.g., an Rx beam sweep from a set of beams(shown, in the top rows of U1 and U2, as ovals rotated in acounter-clockwise direction indicated by the dashed arrow). Procedure U2may be used to enable the base station to adjust its Rx beam when the UEuses a fixed Tx beam. The UE and/or the base station may performprocedure U2 using a smaller set of beams than is used in procedure P1,or using narrower beams than the beams used in procedure P1. This may bereferred to as beam refinement The UE may perform procedure U3 to adjustits Tx beam when the base station uses a fixed Rx beam.

A UE may initiate a beam failure recovery (BFR) procedure based ondetecting a beam failure. The UE may transmit a BFR request (e.g., apreamble, a UCI, an SR, a MAC CE, and/or the like) based on theinitiating of the BFR procedure. The UE may detect the beam failurebased on a determination that a quality of beam pair link(s) of anassociated control channel is unsatisfactory (e.g., having an error ratehigher than an error rate threshold, a received signal power lower thana received signal power threshold, an expiration of a timer, and/or thelike).

The UE may measure a quality of a beam pair link using one or morereference signals (RSs) comprising one or more SS/PBCH blocks, one ormore CSI-RS resources, and/or one or more demodulation reference signals(DMRSs). A quality of the beam pair link may be based on one or more ofa block error rate (BLER), an RSRP value, a signal to interference plusnoise ratio (SINR) value, a reference signal received quality (RSRQ)value, and/or a CSI value measured on RS resources. The base station mayindicate that an RS resource is quasi co-located (QCLed) with one ormore DM-RSs of a channel (e.g., a control channel, a shared datachannel, and/or the like). The RS resource and the one or more DMRSs ofthe channel may be QCLed when the channel characteristics (e.g., Dopplershift, Doppler spread, average delay, delay spread, spatial Rxparameter, fading, and/or the like) from a transmission via the RSresource to the UE are similar or the same as the channelcharacteristics from a transmission via the channel to the UE.

A network (e.g., a gNB and/or an ng-eNB of a network) and/or the UE mayinitiate a random access procedure. A UE in an RRC_IDLE state and/or anRRC_INACTIVE state may initiate the random access procedure to request aconnection setup to a network. The UE may initiate the random accessprocedure from an RRC_CONNECTED state. The UE may initiate the randomaccess procedure to request uplink resources (e.g., for uplinktransmission of an SR when there is no PUCCH resource available) and/oracquire uplink timing (e.g., when uplink synchronization status isnon-synchronized). The UE may initiate the random access procedure torequest one or more system information blocks (SIBs) (e.g., other systeminformation such as SIB2, SIB3, and/or the like). The UE may initiatethe random access procedure for a beam failure recovery request. Anetwork may initiate a random access procedure for a handover and/or forestablishing time alignment for an SCell addition.

FIG. 13A illustrates a four-step contention-based random accessprocedure. Prior to initiation of the procedure, a base station maytransmit a configuration message 1310 to the UE. The procedureillustrated in FIG. 13A comprises transmission of four messages: a Msg 11311, a Msg 2 1312, a Msg 3 1313, and a Msg 4 1314. The Msg 1 1311 mayinclude and/or be referred to as a preamble (or a random accesspreamble). The Msg 2 1312 may include and/or be referred to as a randomaccess response (RAR).

The configuration message 1310 may be transmitted, for example, usingone or more RRC messages. The one or more RRC messages may indicate oneor more random access channel (RACH) parameters to the UE. The one ormore RACH parameters may comprise at least one of following: generalparameters for one or more random access procedures (e.g.,RACH-configGeneral); cell-specific parameters (e.g., RACH-ConfigCommon);and/or dedicated parameters (e.g., RACH-configDedicated). The basestation may broadcast or multicast the one or more RRC messages to oneor more UEs. The one or more RRC messages may be UE-specific (e.g.,dedicated RRC messages transmitted to a UE in an RRC_CONNECTED stateand/or in an RRC_INACTIVE state). The UE may determine, based on the oneor more RACH parameters, a time-frequency resource and/or an uplinktransmit power for transmission of the Msg 1 1311 and/or the Msg 3 1313.Based on the one or more RACH parameters, the UE may determine areception timing and a downlink channel for receiving the Msg 2 1312 andthe Msg 4 1314.

The one or more RACH parameters provided in the configuration message1310 may indicate one or more Physical RACH (PRACH) occasions availablefor transmission of the Msg 1 1311. The one or more PRACH occasions maybe predefined. The one or more RACH parameters may indicate one or moreavailable sets of one or more PRACH occasions (e.g., prach-ConfigIndex).The one or more RACH parameters may indicate an association between (a)one or more PRACH occasions and (b) one or more reference signals. Theone or more RACH parameters may indicate an association between (a) oneor more preambles and (b) one or more reference signals. The one or morereference signals may be SS/PBCH blocks and/or CSI-RSs. For example, theone or more RACH parameters may indicate a number of SS/PBCH blocksmapped to a PRACH occasion and/or a number of preambles mapped to aSS/PBCH blocks.

The one or more RACH parameters provided in the configuration message1310 may be used to determine an uplink transmit power of Msg 1 1311and/or Msg 3 1313. For example, the one or more RACH parameters mayindicate a reference power for a preamble transmission (e.g., a receivedtarget power and/or an initial power of the preamble transmission).There may be one or more power offsets indicated by the one or more RACHparameters. For example, the one or more RACH parameters may indicate: apower ramping step; a power offset between SSB and CSI-RS; a poweroffset between transmissions of the Msg 1 1311 and the Msg 3 1313;and/or a power offset value between preamble groups. The one or moreRACH parameters may indicate one or more thresholds based on which theUE may determine at least one reference signal (e.g., an SSB and/orCSI-RS) and/or an uplink carrier (e.g., a normal uplink (NUL) carrierand/or a supplemental uplink (SUL) carrier).

The Msg 1 1311 may include one or more preamble transmissions (e.g., apreamble transmission and one or more preamble retransmissions). An RRCmessage may be used to configure one or more preamble groups (e.g.,group A and/or group B). A preamble group may comprise one or morepreambles. The UE may determine the preamble group based on a pathlossmeasurement and/or a size of the Msg 3 1313. The UE may measure an RSRPof one or more reference signals (e.g., SSBs and/or CSI-RSs) anddetermine at least one reference signal having an RSRP above an RSRPthreshold (e.g., rsrp-ThresholdSSB and/or rsrp-ThresholdCSI-RS). The UEmay select at least one preamble associated with the one or morereference signals and/or a selected preamble group, for example, if theassociation between the one or more preambles and the at least onereference signal is configured by an RRC message.

The UE may determine the preamble based on the one or more RACHparameters provided in the configuration message 1310. For example, theUE may determine the preamble based on a pathloss measurement, an RSRPmeasurement, and/or a size of the Msg 3 1313. As another example, theone or more RACH parameters may indicate: a preamble format; a maximumnumber of preamble transmissions; and/or one or more thresholds fordetermining one or more preamble groups (e.g., group A and group B). Abase station may use the one or more RACH parameters to configure the UEwith an association between one or more preambles and one or morereference signals (e.g., SSBs and/or CSI-RSs). If the association isconfigured, the UE may determine the preamble to include in Msg 1 1311based on the association. The Msg 1 1311 may be transmitted to the basestation via one or more PRACH occasions. The UE may use one or morereference signals (e.g., SSBs and/or CSI-RSs) for selection of thepreamble and for determining of the PRACH occasion. One or more RACHparameters (e.g., ra-ssb-OccasionMskIndex and/or ra-OccasionList) mayindicate an association between the PRACH occasions and the one or morereference signals.

The UE may perform a preamble retransmission if no response is receivedfollowing a preamble transmission. The UE may increase an uplinktransmit power for the preamble retransmission. The UE may select aninitial preamble transmit power based on a pathloss measurement and/or atarget received preamble power configured by the network. The UE maydetermine to retransmit a preamble and may ramp up the uplink transmitpower. The UE may receive one or more RACH parameters (e.g.,PREAMBLE_POWER_RAMPING_STEP) indicating a ramping step for the preambleretransmission. The ramping step may be an amount of incrementalincrease in uplink transmit power for a retransmission. The UE may rampup the uplink transmit power if the UE determines a reference signal(e.g., SSB and/or CSI-RS) that is the same as a previous preambletransmission. The UE may count a number of preamble transmissions and/orretransmissions (e.g., PREAMBLE_TRANSMISSION_COUNTER). The UE maydetermine that a random access procedure completed unsuccessfully, forexample, if the number of preamble transmissions exceeds a thresholdconfigured by the one or more RACH parameters (e.g., preambleTransMax).

The Msg 2 1312 received by the UE may include an RAR. In some scenarios,the Msg 2 1312 may include multiple RARs corresponding to multiple UEs.The Msg 2 1312 may be received after or in response to the transmittingof the Msg 1 1311. The Msg 2 1312 may be scheduled on the DL-SCH andindicated on a PDCCH using a random access RNTI (RA-RNTI). The Msg 21312 may indicate that the Msg 1 1311 was received by the base station.The Msg 2 1312 may include a time-alignment command that may be used bythe UE to adjust the UE's transmission timing, a scheduling grant fortransmission of the Msg 3 1313, and/or a Temporary Cell RNTI (TC-RNTI).After transmitting a preamble, the UE may start a time window (e.g.,ra-ResponseWindow) to monitor a PDCCH for the Msg 2 1312. The UE maydetermine when to start the time window based on a PRACH occasion thatthe UE uses to transmit the preamble. For example, the UE may start thetime window one or more symbols after a last symbol of the preamble(e.g., at a first PDCCH occasion from an end of a preambletransmission). The one or more symbols may be determined based on anumerology. The PDCCH may be in a common search space (e.g., aType1-PDCCH common search space) configured by an RRC message. The UEmay identify the RAR based on a Radio Network Temporary Identifier(RNTI). RNTIs may be used depending on one or more events initiating therandom access procedure. The UE may use random access RNTI (RA-RNTI).The RA-RNTI may be associated with PRACH occasions in which the UEtransmits a preamble. For example, the UE may determine the RA-RNTIbased on: an OFDM symbol index; a slot index; a frequency domain index;and/or a UL carrier indicator of the PRACH occasions. An example ofRA-RNTI may be as follows:

RA-RNTI=1+s_id+14×t_id+14×80×f_id+14×80×8×ul_carrier_id

where s_id may be an index of a first OFDM symbol of the PRACH occasion(e.g., 0≤s_id<14), t_id may be an index of a first slot of the PRACHoccasion in a system frame (e.g., 0≤t_id<80), f_id may be an index ofthe PRACH occasion in the frequency domain (e.g., 0≤f_id<8), andul_carrier_id may be a UL carrier used for a preamble transmission(e.g., 0 for an NUL carrier, and 1 for an SUL carrier).

The UE may transmit the Msg 3 1313 in response to a successful receptionof the Msg 2 1312 (e.g., using resources identified in the Msg 2 1312).The Msg 3 1313 may be used for contention resolution in, for example,the contention-based random access procedure illustrated in FIG. 13A. Insome scenarios, a plurality of UEs may transmit a same preamble to abase station and the base station may provide an RAR that corresponds toa UE. Collisions may occur if the plurality of UEs interpret the RAR ascorresponding to themselves. Contention resolution (e.g., using the Msg3 1313 and the Msg 4 1314) may be used to increase the likelihood thatthe UE does not incorrectly use an identity of another the UE. Toperform contention resolution, the UE may include a device identifier inthe Msg 3 1313 (e.g., a C-RNTI if assigned, a TC-RNTI included in theMsg 2 1312, and/or any other suitable identifier).

The Msg 4 1314 may be received after or in response to the transmittingof the Msg 3 1313. If a C-RNTI was included in the Msg 3 1313, the basestation will address the UE on the PDCCH using the C-RNTI. If the UE'sunique C-RNTI is detected on the PDCCH, the random access procedure isdetermined to be successfully completed. If a TC-RNTI is included in theMsg 3 1313 (e.g., if the UE is in an RRC_IDLE state or not otherwiseconnected to the base station), Msg 4 1314 will be received using aDL-SCH associated with the TC-RNTI. If a MAC PDU is successfully decodedand a MAC PDU comprises the UE contention resolution identity MAC CEthat matches or otherwise corresponds with the CCCH SDU sent (e.g.,transmitted) in Msg 3 1313, the UE may determine that the contentionresolution is successful and/or the UE may determine that the randomaccess procedure is successfully completed.

The UE may be configured with a supplementary uplink (SUL) carrier and anormal uplink (NUL) carrier. An initial access (e.g., random accessprocedure) may be supported in an uplink carrier. For example, a basestation may configure the UE with two separate RACH configurations: onefor an SUL carrier and the other for an NUL carrier. For random accessin a cell configured with an SUL carrier, the network may indicate whichcarrier to use (NUL or SUL). The UE may determine the SUL carrier, forexample, if a measured quality of one or more reference signals is lowerthan a broadcast threshold. Uplink transmissions of the random accessprocedure (e.g., the Msg 1 1311 and/or the Msg 3 1313) may remain on theselected carrier. The UE may switch an uplink carrier during the randomaccess procedure (e.g., between the Msg 1 1311 and the Msg 3 1313) inone or more cases. For example, the UE may determine and/or switch anuplink carrier for the Msg 1 1311 and/or the Msg 3 1313 based on achannel clear assessment (e.g., a listen-before-talk).

FIG. 13B illustrates a two-step contention-free random access procedure.Similar to the four-step contention-based random access procedureillustrated in FIG. 13A, a base station may, prior to initiation of theprocedure, transmit a configuration message 1320 to the UE. Theconfiguration message 1320 may be analogous in some respects to theconfiguration message 1310. The procedure illustrated in FIG. 13Bcomprises transmission of two messages: a Msg 1 1321 and a Msg 2 1322.The Msg 1 1321 and the Msg 2 1322 may be analogous in some respects tothe Msg 1 1311 and a Msg 2 1312 illustrated in FIG. 13A, respectively.As will be understood from FIGS. 13A and 13B, the contention-free randomaccess procedure may not include messages analogous to the Msg 3 1313and/or the Msg 4 1314.

The contention-free random access procedure illustrated in FIG. 13B maybe initiated for a beam failure recovery, other SI request, SCelladdition, and/or handover. For example, a base station may indicate orassign to the UE the preamble to be used for the Msg 1 1321. The UE mayreceive, from the base station via PDCCH and/or RRC, an indication of apreamble (e.g., ra-PreambleIndex).

After transmitting a preamble, the UE may start a time window (e.g.,ra-ResponseWindow) to monitor a PDCCH for the RAR. In the event of abeam failure recovery request, the base station may configure the UEwith a separate time window and/or a separate PDCCH in a search spaceindicated by an RRC message (e.g., recoverySearchSpaceId). The UE maymonitor for a PDCCH transmission addressed to a Cell RNTI (C-RNTI) onthe search space. In the contention-free random access procedureillustrated in FIG. 13B, the UE may determine that a random accessprocedure successfully completes after or in response to transmission ofMsg 1 1321 and reception of a corresponding Msg 2 1322. The UE maydetermine that a random access procedure successfully completes, forexample, if a PDCCH transmission is addressed to a C-RNTI. The UE maydetermine that a random access procedure successfully completes, forexample, if the UE receives an RAR comprising a preamble identifiercorresponding to a preamble transmitted by the UE and/or the RARcomprises a MAC sub-PDU with the preamble identifier. The UE maydetermine the response as an indication of an acknowledgement for an SIrequest.

FIG. 13C illustrates another two-step random access procedure. Similarto the random access procedures illustrated in FIGS. 13A and 13B, a basestation may, prior to initiation of the procedure, transmit aconfiguration message 1330 to the UE. The configuration message 1330 maybe analogous in some respects to the configuration message 1310 and/orthe configuration message 1320. The procedure illustrated in FIG. 13Ccomprises transmission of two messages: a Msg A 1331 and a Msg B 1332.

Msg A 1331 may be transmitted in an uplink transmission by the UE. Msg A1331 may comprise one or more transmissions of a preamble 1341 and/orone or more transmissions of a transport block 1342. The transport block1342 may comprise contents that are similar and/or equivalent to thecontents of the Msg 3 1313 illustrated in FIG. 13A. The transport block1342 may comprise UCI (e.g., an SR, a HARQ ACK/NACK, and/or the like).The UE may receive the Msg B 1332 after or in response to transmittingthe Msg A 1331. The Msg B 1332 may comprise contents that are similarand/or equivalent to the contents of the Msg 2 1312 (e.g., an RAR)illustrated in FIGS. 13A and 13B and/or the Msg 4 1314 illustrated inFIG. 13A.

The UE may initiate the two-step random access procedure in FIG. 13C forlicensed spectrum and/or unlicensed spectrum. The UE may determine,based on one or more factors, whether to initiate the two-step randomaccess procedure. The one or more factors may be: a radio accesstechnology in use (e.g., LTE, NR, and/or the like); whether the UE hasvalid TA or not; a cell size; the UE's RRC state; a type of spectrum(e.g., licensed vs. unlicensed); and/or any other suitable factors.

The UE may determine, based on two-step RACH parameters included in theconfiguration message 1330, a radio resource and/or an uplink transmitpower for the preamble 1341 and/or the transport block 1342 included inthe Msg A 1331. The RACH parameters may indicate a modulation and codingschemes (MCS), a time-frequency resource, and/or a power control for thepreamble 1341 and/or the transport block 1342. A time-frequency resourcefor transmission of the preamble 1341 (e.g., a PRACH) and atime-frequency resource for transmission of the transport block 1342(e.g., a PUSCH) may be multiplexed using FDM, TDM, and/or CDM. The RACHparameters may enable the UE to determine a reception timing and adownlink channel for monitoring for and/or receiving Msg B 1332.

The transport block 1342 may comprise data (e.g., delay-sensitive data),an identifier of the UE, security information, and/or device information(e.g., an International Mobile Subscriber Identity (IMSI)). The basestation may transmit the Msg B 1332 as a response to the Msg A 1331. TheMsg B 1332 may comprise at least one of following: a preambleidentifier; a timing advance command; a power control command; an uplinkgrant (e.g., a radio resource assignment and/or an MCS); a UE identifierfor contention resolution; and/or an RNTI (e.g., a C-RNTI or a TC-RNTI).The UE may determine that the two-step random access procedure issuccessfully completed if: a preamble identifier in the Msg B 1332 ismatched to a preamble transmitted by the UE; and/or the identifier ofthe UE in Msg B 1332 is matched to the identifier of the UE in the Msg A1331 (e.g., the transport block 1342).

A UE and a base station may exchange control signaling. The controlsignaling may be referred to as L1/L2 control signaling and mayoriginate from the PHY layer (e.g., layer 1) and/or the MAC layer (e.g.,layer 2). The control signaling may comprise downlink control signalingtransmitted from the base station to the UE and/or uplink controlsignaling transmitted from the UE to the base station.

The downlink control signaling may comprise: a downlink schedulingassignment; an uplink scheduling grant indicating uplink radio resourcesand/or a transport format; a slot format information; a preemptionindication; a power control command; and/or any other suitablesignaling. The UE may receive the downlink control signaling in apayload transmitted by the base station on a physical downlink controlchannel (PDCCH). The payload transmitted on the PDCCH may be referred toas downlink control information (DCI). In some scenarios, the PDCCH maybe a group common PDCCH (GC-PDCCH) that is common to a group of UEs.

A base station may attach one or more cyclic redundancy check (CRC)parity bits to a DCI in order to facilitate detection of transmissionerrors. When the DCI is intended for a UE (or a group of the UEs), thebase station may scramble the CRC parity bits with an identifier of theUE (or an identifier of the group of the UEs). Scrambling the CRC paritybits with the identifier may comprise Modulo-2 addition (or an exclusiveOR operation) of the identifier value and the CRC parity bits. Theidentifier may comprise a 16-bit value of a radio network temporaryidentifier (RNTI).

DCIs may be used for different purposes. A purpose may be indicated bythe type of RNTI used to scramble the CRC parity bits. For example, aDCI having CRC parity bits scrambled with a paging RNTI (P-RNTI) mayindicate paging information and/or a system information changenotification. The P-RNTI may be predefined as “FFFE” in hexadecimal. ADCI having CRC parity bits scrambled with a system information RNTI(SI-RNTI) may indicate a broadcast transmission of the systeminformation. The SI-RNTI may be predefined as “FFFF” in hexadecimal. ADCI having CRC parity bits scrambled with a random access RNTI (RA-RNTI)may indicate a random access response (RAR). A DCI having CRC paritybits scrambled with a cell RNTI (C-RNTI) may indicate a dynamicallyscheduled unicast transmission and/or a triggering of PDCCH-orderedrandom access. A DCI having CRC parity bits scrambled with a temporarycell RNTI (TC-RNTI) may indicate a contention resolution (e.g., a Msg 3analogous to the Msg 3 1313 illustrated in FIG. 13A). Other RNTIsconfigured to the UE by a base station may comprise a ConfiguredScheduling RNTI (CS-RNTI), a Transmit Power Control-PUCCH RNTI(TPC-PUCCH-RNTI), a Transmit Power Control-PUSCH RNTI (TPC-PUSCH-RNTI),a Transmit Power Control-SRS RNTI (TPC-SRS-RNTI), an Interruption RNTI(INT-RNTI), a Slot Format Indication RNTI (SFI-RNTI), a Semi-PersistentCSI RNTI (SP-CSI-RNTI), a Modulation and Coding Scheme Cell RNTI(MCS-C-RNTI), and/or the like.

Depending on the purpose and/or content of a DCI, the base station maytransmit the DCIs with one or more DCI formats. For example, DCI format00 may be used for scheduling of PUSCH in a cell. DCI format 0_0 may bea fallback DCI format (e.g., with compact DCI payloads). DCI format 0_1may be used for scheduling of PUSCH in a cell (e.g., with more DCIpayloads than DCI format 0_0). DCI format 1_0 may be used for schedulingof PDSCH in a cell. DCI format 1_0 may be a fallback DCI format (e.g.,with compact DCI payloads). DCI format 1_1 may be used for scheduling ofPDSCH in a cell (e.g., with more DCI payloads than DCI format 1_0). DCIformat 2_0 may be used for providing a slot format indication to a groupof UEs. DCI format 2_1 may be used for notifying a group of UEs of aphysical resource block and/or OFDM symbol where the UE may assume notransmission is intended to the UE. DCI format 2_2 may be used fortransmission of a transmit power control (TPC) command for PUCCH orPUSCH. DCI format 2_3 may be used for transmission of a group of TPCcommands for SRS transmissions by one or more UEs. DCI format(s) for newfunctions may be defined in future releases. DCI formats may havedifferent DCI sizes, or may share the same DCI size.

After scrambling a DCI with a RNTI, the base station may process the DCIwith channel coding (e.g., polar coding), rate matching, scramblingand/or QPSK modulation. A base station may map the coded and modulatedDCI on resource elements used and/or configured for a PDCCH. Based on apayload size of the DCI and/or a coverage of the base station, the basestation may transmit the DCI via a PDCCH occupying a number ofcontiguous control channel elements (CCEs). The number of the contiguousCCEs (referred to as aggregation level) may be 1, 2, 4, 8, 16, and/orany other suitable number. A CCE may comprise a number (e.g., 6) ofresource-element groups (REGs). A REG may comprise a resource block inan OFDM symbol. The mapping of the coded and modulated DCI on theresource elements may be based on mapping of CCEs and REGs (e.g.,CCE-to-REG mapping).

FIG. 14A illustrates an example of CORESET configurations for abandwidth part. The base station may transmit a DCI via a PDCCH on oneor more control resource sets (CORESETs). A CORESET may comprise atime-frequency resource in which the UE tries to decode a DCI using oneor more search spaces. The base station may configure a CORESET in thetime-frequency domain. In the example of FIG. 14A, a first CORESET 1401and a second CORESET 1402 occur at the first symbol in a slot. The firstCORESET 1401 overlaps with the second CORESET 1402 in the frequencydomain. A third CORESET 1403 occurs at a third symbol in the slot. Afourth CORESET 1404 occurs at the seventh symbol in the slot. CORESETsmay have a different number of resource blocks in frequency domain.

FIG. 14B illustrates an example of a CCE-to-REG mapping for DCItransmission on a CORESET and PDCCH processing. The CCE-to-REG mappingmay be an interleaved mapping (e.g., for the purpose of providingfrequency diversity) or a non-interleaved mapping (e.g., for thepurposes of facilitating interference coordination and/orfrequency-selective transmission of control channels). The base stationmay perform different or same CCE-to-REG mapping on different CORESETs.A CORESET may be associated with a CCE-to-REG mapping by RRCconfiguration. A CORESET may be configured with an antenna port quasico-location (QCL) parameter. The antenna port QCL parameter may indicateQCL information of a demodulation reference signal (DMRS) for PDCCHreception in the CORESET.

The base station may transmit, to the UE, RRC messages comprisingconfiguration parameters of one or more CORESETs and one or more searchspace sets. The configuration parameters may indicate an associationbetween a search space set and a CORESET. A search space set maycomprise a set of PDCCH candidates formed by CCEs at a given aggregationlevel. The configuration parameters may indicate: a number of PDCCHcandidates to be monitored per aggregation level; a PDCCH monitoringperiodicity and a PDCCH monitoring pattern; one or more DCI formats tobe monitored by the UE; and/or whether a search space set is a commonsearch space set or a UE-specific search space set. A set of CCEs in thecommon search space set may be predefined and known to the UE. A set ofCCEs in the UE-specific search space set may be configured based on theUE's identity (e.g., C-RNTI).

As shown in FIG. 14B, the UE may determine a time-frequency resource fora CORESET based on RRC messages. The UE may determine a CCE-to-REGmapping (e.g., interleaved or non-interleaved, and/or mappingparameters) for the CORESET based on configuration parameters of theCORESET. The UE may determine a number (e.g., at most 10) of searchspace sets configured on the CORESET based on the RRC messages. The UEmay monitor a set of PDCCH candidates according to configurationparameters of a search space set. The UE may monitor a set of PDCCHcandidates in one or more CORESETs for detecting one or more DCIs.Monitoring may comprise decoding one or more PDCCH candidates of the setof the PDCCH candidates according to the monitored DCI formats.Monitoring may comprise decoding a DCI content of one or more PDCCHcandidates with possible (or configured) PDCCH locations, possible (orconfigured) PDCCH formats (e.g., number of CCEs, number of PDCCHcandidates in common search spaces, and/or number of PDCCH candidates inthe UE-specific search spaces) and possible (or configured) DCI formats.The decoding may be referred to as blind decoding. The UE may determinea DCI as valid for the UE, in response to CRC checking (e.g., scrambledbits for CRC parity bits of the DCI matching a RNTI value). The UE mayprocess information contained in the DCI (e.g., a scheduling assignment,an uplink grant, power control, a slot format indication, a downlinkpreemption, and/or the like).

The UE may transmit uplink control signaling (e.g., uplink controlinformation (UCI)) to a base station. The uplink control signaling maycomprise hybrid automatic repeat request (HARQ) acknowledgements forreceived DL-SCH transport blocks. The UE may transmit the HARQacknowledgements after receiving a DL-SCH transport block. Uplinkcontrol signaling may comprise channel state information (CSI)indicating channel quality of a physical downlink channel. The UE maytransmit the CSI to the base station. The base station, based on thereceived CSI, may determine transmission format parameters (e.g.,comprising multi-antenna and beamforming schemes) for a downlinktransmission. Uplink control signaling may comprise scheduling requests(SR). The UE may transmit an SR indicating that uplink data is availablefor transmission to the base station. The UE may transmit a UCI (e.g.,HARQ acknowledgements (HARQ-ACK), CSI report, SR, and the like) via aphysical uplink control channel (PUCCH) or a physical uplink sharedchannel (PUSCH). The UE may transmit the uplink control signaling via aPUCCH using one of several PUCCH formats.

There may be five PUCCH formats and the UE may determine a PUCCH formatbased on a size of the UCI (e.g., a number of uplink symbols of UCItransmission and a number of UCI bits). PUCCH format 0 may have a lengthof one or two OFDM symbols and may include two or fewer bits. The UE maytransmit UCI in a PUCCH resource using PUCCH format 0 if thetransmission is over one or two symbols and the number of HARQ-ACKinformation bits with positive or negative SR (HARQ-ACK/SR bits) is oneor two. PUCCH format 1 may occupy a number between four and fourteenOFDM symbols and may include two or fewer bits. The UE may use PUCCHformat 1 if the transmission is four or more symbols and the number ofHARQ-ACK/SR bits is one or two. PUCCH format 2 may occupy one or twoOFDM symbols and may include more than two bits. The UE may use PUCCHformat 2 if the transmission is over one or two symbols and the numberof UCI bits is two or more. PUCCH format 3 may occupy a number betweenfour and fourteen OFDM symbols and may include more than two bits. TheUE may use PUCCH format 3 if the transmission is four or more symbols,the number of UCI bits is two or more and PUCCH resource does notinclude an orthogonal cover code. PUCCH format 4 may occupy a numberbetween four and fourteen OFDM symbols and may include more than twobits. The UE may use PUCCH format 4 if the transmission is four or moresymbols, the number of UCI bits is two or more and the PUCCH resourceincludes an orthogonal cover code.

The base station may transmit configuration parameters to the UE for aplurality of PUCCH resource sets using, for example, an RRC message. Theplurality of PUCCH resource sets (e.g., up to four sets) may beconfigured on an uplink BWP of a cell. A PUCCH resource set may beconfigured with a PUCCH resource set index, a plurality of PUCCHresources with a PUCCH resource being identified by a PUCCH resourceidentifier (e.g., pucch-Resourceid), and/or a number (e.g. a maximumnumber) of UCI information bits the UE may transmit using one of theplurality of PUCCH resources in the PUCCH resource set. When configuredwith a plurality of PUCCH resource sets, the UE may select one of theplurality of PUCCH resource sets based on a total bit length of the UCIinformation bits (e.g., HARQ-ACK, SR, and/or CSI). If the total bitlength of UCI information bits is two or fewer, the UE may select afirst PUCCH resource set having a PUCCH resource set index equal to “0”.If the total bit length of UCI information bits is greater than two andless than or equal to a first configured value, the UE may select asecond PUCCH resource set having a PUCCH resource set index equal to“1”. If the total bit length of UCI information bits is greater than thefirst configured value and less than or equal to a second configuredvalue, the UE may select a third PUCCH resource set having a PUCCHresource set index equal to “2”. If the total bit length of UCIinformation bits is greater than the second configured value and lessthan or equal to a third value (e.g., 1406), the UE may select a fourthPUCCH resource set having a PUCCH resource set index equal to “3”.

After determining a PUCCH resource set from a plurality of PUCCHresource sets, the UE may determine a PUCCH resource from the PUCCHresource set for UCI (HARQ-ACK, CSI, and/or SR) transmission. The UE maydetermine the PUCCH resource based on a PUCCH resource indicator in aDCI (e.g., with a DCI format 1_0 or DCI for 1_1) received on a PDCCH. Athree-bit PUCCH resource indicator in the DCI may indicate one of eightPUCCH resources in the PUCCH resource set. Based on the PUCCH resourceindicator, the UE may transmit the UCI (HARQ-ACK, CSI and/or SR) using aPUCCH resource indicated by the PUCCH resource indicator in the DCI.

FIG. 15 illustrates an example of a wireless device 1502 incommunication with a base station 1504 in accordance with embodiments ofthe present disclosure. The wireless device 1502 and base station 1504may be part of a mobile communication network, such as the mobilecommunication network 100 illustrated in FIG. 1A, the mobilecommunication network 150 illustrated in FIG. 1B, or any othercommunication network. Only one wireless device 1502 and one basestation 1504 are illustrated in FIG. 15 , but it will be understood thata mobile communication network may include more than one UE and/or morethan one base station, with the same or similar configuration as thoseshown in FIG. 15 .

The base station 1504 may connect the wireless device 1502 to a corenetwork (not shown) through radio communications over the air interface(or radio interface) 1506. The communication direction from the basestation 1504 to the wireless device 1502 over the air interface 1506 isknown as the downlink, and the communication direction from the wirelessdevice 1502 to the base station 1504 over the air interface is known asthe uplink. Downlink transmissions may be separated from uplinktransmissions using FDD, TDD, and/or some combination of the twoduplexing techniques.

In the downlink, data to be sent to the wireless device 1502 from thebase station 1504 may be provided to the processing system 1508 of thebase station 1504. The data may be provided to the processing system1508 by, for example, a core network. In the uplink, data to be sent tothe base station 1504 from the wireless device 1502 may be provided tothe processing system 1518 of the wireless device 1502. The processingsystem 1508 and the processing system 1518 may implement layer 3 andlayer 2 OSI functionality to process the data for transmission. Layer 2may include an SDAP layer, a PDCP layer, an RLC layer, and a MAC layer,for example, with respect to FIG. 2A, FIG. 2B, FIG. 3 , and FIG. 4A.Layer 3 may include an RRC layer as with respect to FIG. 2B.

After being processed by processing system 1508, the data to be sent tothe wireless device 1502 may be provided to a transmission processingsystem 1510 of base station 1504. Similarly, after being processed bythe processing system 1518, the data to be sent to base station 1504 maybe provided to a transmission processing system 1520 of the wirelessdevice 1502. The transmission processing system 1510 and thetransmission processing system 1520 may implement layer 1 OSIfunctionality. Layer 1 may include a PHY layer with respect to FIG. 2A,FIG. 2B, FIG. 3 , and FIG. 4A. For transmit processing, the PHY layermay perform, for example, forward error correction coding of transportchannels, interleaving, rate matching, mapping of transport channels tophysical channels, modulation of physical channel, multiple-inputmultiple-output (MIMO) or multi-antenna processing, and/or the like.

At the base station 1504, a reception processing system 1512 may receivethe uplink transmission from the wireless device 1502. At the wirelessdevice 1502, a reception processing system 1522 may receive the downlinktransmission from base station 1504. The reception processing system1512 and the reception processing system 1522 may implement layer 1 OSIfunctionality. Layer 1 may include a PHY layer with respect to FIG. 2A,FIG. 2B, FIG. 3 , and FIG. 4A. For receive processing, the PHY layer mayperform, for example, error detection, forward error correctiondecoding, deinterleaving, demapping of transport channels to physicalchannels, demodulation of physical channels, MIMO or multi-antennaprocessing, and/or the like.

As shown in FIG. 15 , a wireless device 1502 and the base station 1504may include multiple antennas. The multiple antennas may be used toperform one or more MIMO or multi-antenna techniques, such as spatialmultiplexing (e.g., single-user MIMO or multi-user MIMO),transmit/receive diversity, and/or beamforming. In other examples, thewireless device 1502 and/or the base station 1504 may have a singleantenna.

The processing system 1508 and the processing system 1518 may beassociated with a memory 1514 and a memory 1524, respectively. Memory1514 and memory 1524 (e.g., one or more non-transitory computer readablemediums) may store computer program instructions or code that may beexecuted by the processing system 1508 and/or the processing system 1518to carry out one or more of the functionalities discussed in the presentapplication. Although not shown in FIG. 15 , the transmission processingsystem 1510, the transmission processing system 1520, the receptionprocessing system 1512, and/or the reception processing system 1522 maybe coupled to a memory (e.g., one or more non-transitory computerreadable mediums) storing computer program instructions or code that maybe executed to carry out one or more of their respectivefunctionalities.

The processing system 1508 and/or the processing system 1518 maycomprise one or more controllers and/or one or more processors. The oneor more controllers and/or one or more processors may comprise, forexample, a general-purpose processor, a digital signal processor (DSP),a microcontroller, an application specific integrated circuit (ASIC), afield programmable gate array (FPGA) and/or other programmable logicdevice, discrete gate and/or transistor logic, discrete hardwarecomponents, an on-board unit, or any combination thereof. The processingsystem 1508 and/or the processing system 1518 may perform at least oneof signal coding/processing, data processing, power control,input/output processing, and/or any other functionality that may enablethe wireless device 1502 and the base station 1504 to operate in awireless environment.

The processing system 1508 and/or the processing system 1518 may beconnected to one or more peripherals 1516 and one or more peripherals1526, respectively. The one or more peripherals 1516 and the one or moreperipherals 1526 may include software and/or hardware that providefeatures and/or functionalities, for example, a speaker, a microphone, akeypad, a display, a touchpad, a power source, a satellite transceiver,a universal serial bus (USB) port, a hands-free headset, a frequencymodulated (FM) radio unit, a media player, an Internet browser, anelectronic control unit (e.g., for a motor vehicle), and/or one or moresensors (e.g., an accelerometer, a gyroscope, a temperature sensor, aradar sensor, a lidar sensor, an ultrasonic sensor, a light sensor, acamera, and/or the like). The processing system 1508 and/or theprocessing system 1518 may receive user input data from and/or provideuser output data to the one or more peripherals 1516 and/or the one ormore peripherals 1526. The processing system 1518 in the wireless device1502 may receive power from a power source and/or may be configured todistribute the power to the other components in the wireless device1502. The power source may comprise one or more sources of power, forexample, a battery, a solar cell, a fuel cell, or any combinationthereof. The processing system 1508 and/or the processing system 1518may be connected to a GPS chipset 1517 and a GPS chipset 1527,respectively. The GPS chipset 1517 and the GPS chipset 1527 may beconfigured to provide geographic location information of the wirelessdevice 1502 and the base station 1504, respectively.

FIG. 16A illustrates an example structure for uplink transmission. Abaseband signal representing a physical uplink shared channel mayperform one or more functions. The one or more functions may comprise atleast one of: scrambling; modulation of scrambled bits to generatecomplex-valued symbols; mapping of the complex-valued modulation symbolsonto one or several transmission layers; transform precoding to generatecomplex-valued symbols; precoding of the complex-valued symbols; mappingof precoded complex-valued symbols to resource elements; generation ofcomplex-valued time-domain Single Carrier-Frequency Division MultipleAccess (SC-FDMA) or CP-OFDM signal for an antenna port; and/or the like.In an example, when transform precoding is enabled, a SC-FDMA signal foruplink transmission may be generated. In an example, when transformprecoding is not enabled, an CP-OFDM signal for uplink transmission maybe generated by FIG. 16A. These functions are illustrated as examplesand it is anticipated that other mechanisms may be implemented invarious embodiments.

FIG. 16B illustrates an example structure for modulation andup-conversion of a baseband signal to a carrier frequency. The basebandsignal may be a complex-valued SC-FDMA or CP-OFDM baseband signal for anantenna port and/or a complex-valued Physical Random Access Channel(PRACH) baseband signal. Filtering may be employed prior totransmission.

FIG. 16C illustrates an example structure for downlink transmissions. Abaseband signal representing a physical downlink channel may perform oneor more functions. The one or more functions may comprise: scrambling ofcoded bits in a codeword to be transmitted on a physical channel;modulation of scrambled bits to generate complex-valued modulationsymbols; mapping of the complex-valued modulation symbols onto one orseveral transmission layers; precoding of the complex-valued modulationsymbols on a layer for transmission on the antenna ports; mapping ofcomplex-valued modulation symbols for an antenna port to resourceelements; generation of complex-valued time-domain OFDM signal for anantenna port; and/or the like. These functions are illustrated asexamples and it is anticipated that other mechanisms may be implementedin various embodiments.

FIG. 16D illustrates another example structure for modulation andup-conversion of a baseband signal to a carrier frequency. The basebandsignal may be a complex-valued OFDM baseband signal for an antenna port.Filtering may be employed prior to transmission.

A wireless device may receive from a base station one or more messages(e.g. RRC messages) comprising configuration parameters of a pluralityof cells (e.g. primary cell, secondary cell). The wireless device maycommunicate with at least one base station (e.g. two or more basestations in dual-connectivity) via the plurality of cells. The one ormore messages (e.g. as a part of the configuration parameters) maycomprise parameters of physical, MAC, RLC, PCDP, SDAP, RRC layers forconfiguring the wireless device. For example, the configurationparameters may comprise parameters for configuring physical and MAClayer channels, bearers, etc. For example, the configuration parametersmay comprise parameters indicating values of timers for physical, MAC,RLC, PCDP, SDAP, RRC layers, and/or communication channels.

A timer may begin running once it is started and continue running untilit is stopped or until it expires. A timer may be started if it is notrunning or restarted if it is running. A timer may be associated with avalue (e.g. the timer may be started or restarted from a value or may bestarted from zero and expire once it reaches the value). The duration ofa timer may not be updated until the timer is stopped or expires (e.g.,due to BWP switching). A timer may be used to measure a timeperiod/window for a process. When the specification refers to animplementation and procedure related to one or more timers, it will beunderstood that there are multiple ways to implement the one or moretimers. For example, it will be understood that one or more of themultiple ways to implement a timer may be used to measure a timeperiod/window for the procedure. For example, a random access responsewindow timer may be used for measuring a window of time for receiving arandom access response. In an example, instead of starting and expiry ofa random access response window timer, the time difference between twotime stamps may be used. When a timer is restarted, a process formeasurement of time window may be restarted. Other exampleimplementations may be provided to restart a measurement of a timewindow. FIG. 17 illustrates examples of device-to-device (D2D)communication, in which there is a direct communication between wirelessdevices. In an example, D2D communication may be performed via asidelink (SL). The wireless devices may exchange sidelink communicationsvia a sidelink interface (e.g., a PC5 interface). Sidelink differs fromuplink (in which a wireless device communicates to a base station) anddownlink (in which a base station communicates to a wireless device). Awireless device and a base station may exchange uplink and/or downlinkcommunications via a user plane interface (e.g., a Uu interface).

As shown in the figure, wireless device #1 and wireless device #2 may bein a coverage area of base station #1. For example, both wireless device#1 and wireless device #2 may communicate with the base station #1 via aUu interface. Wireless device #3 may be in a coverage area of basestation #2. Base station #1 and base station #2 may share a network andmay jointly provide a network coverage area. Wireless device #4 andwireless device #5 may be outside of the network coverage area.

In-coverage D2D communication may be performed when two wireless devicesshare a network coverage area. Wireless device #1 and wireless device #2are both in the coverage area of base station #1. Accordingly, they mayperform an in-coverage intra-cell D2D communication, labeled as sidelinkA. Wireless device #2 and wireless device #3 are in the coverage areasof different base stations, but share the same network coverage area.Accordingly, they may perform an in-coverage inter-cell D2Dcommunication, labeled as sidelink B. Partial-coverage D2Dcommunications may be performed when one wireless device is within thenetwork coverage area and the other wireless device is outside thenetwork coverage area. Wireless device #3 and wireless device #4 mayperform a partial-coverage D2D communication, labeled as sidelink C.Out-of-coverage D2D communications may be performed when both wirelessdevices are outside of the network coverage area. Wireless device #4 andwireless device #5 may perform an out-of-coverage D2D communication,labeled as sidelink D.

Sidelink communications may be configured using physical channels, forexample, a physical sidelink broadcast channel (PSBCH), a physicalsidelink feedback channel (PSFCH), a physical sidelink discovery channel(PSDCH), a physical sidelink control channel (PSCCH), and/or a physicalsidelink shared channel (PSSCH). PSBCH may be used by a first wirelessdevice to send broadcast information to a second wireless device. PSBCHmay be similar in some respects to PBCH. The broadcast information maycomprise, for example, a slot format indication, resource poolinformation, a sidelink system frame number, or any other suitablebroadcast information. PSFCH may be used by a first wireless device tosend feedback information to a second wireless device. The feedbackinformation may comprise, for example, HARQ feedback information. PSDCHmay be used by a first wireless device to send discovery information toa second wireless device. The discovery information may be used by awireless device to signal its presence and/or the availability ofservices to other wireless devices in the area. PSCCH may be used by afirst wireless device to send sidelink control information (SCI) to asecond wireless device. PSCCH may be similar in some respects to PDCCHand/or PUCCH. The control information may comprise, for example,time/frequency resource allocation information (RB size, a number ofretransmissions, etc.), demodulation related information (DMRS, MCS, RV,etc.), identifying information for a transmitting wireless device and/ora receiving wireless device, a process identifier (HARQ, etc.), or anyother suitable control information. The PSCCH may be used to allocate,prioritize, and/or reserve sidelink resources for sidelinktransmissions. PSSCH may be used by a first wireless device to sendand/or relay data and/or network information to a second wirelessdevice. PSSCH may be similar in some respects to PDSCH and/or PUSCH.Each of the sidelink channels may be associated with one or moredemodulation reference signals. Sidelink operations may utilize sidelinksynchronization signals to establish a timing of sidelink operations.Wireless devices configured for sidelink operations may send sidelinksynchronization signals, for example, with the PSBCH. The sidelinksynchronization signals may include primary sidelink synchronizationsignals (PSSS) and secondary sidelink synchronization signals (SSSS).

Sidelink resources may be configured to a wireless device in anysuitable manner. A wireless device may be pre-configured for sidelink,for example, pre-configured with sidelink resource information.Additionally or alternatively, a network may broadcast systeminformation relating to a resource pool for sidelink. Additionally oralternatively, a network may configure a particular wireless device witha dedicated sidelink configuration. The configuration may identifysidelink resources to be used for sidelink operation (e.g., configure asidelink band combination).

The wireless device may operate in different modes, for example, anassisted mode (which may be referred to as mode 1) or an autonomous mode(which may be referred to as mode 2). Mode selection may be based on acoverage status of the wireless device, a radio resource control statusof the wireless device, information and/or instructions from thenetwork, and/or any other suitable factors. For example, if the wirelessdevice is idle or inactive, or if the wireless device is outside ofnetwork coverage, the wireless device may select to operate inautonomous mode. For example, if the wireless device is in a connectedmode (e.g., connected to a base station), the wireless device may selectto operate (or be instructed by the base station to operate) in assistedmode. For example, the network (e.g., a base station) may instruct aconnected wireless device to operate in a particular mode.

In an assisted mode, the wireless device may request scheduling from thenetwork. For example, the wireless device may send a scheduling requestto the network and the network may allocate sidelink resources to thewireless device. Assisted mode may be referred to as network-assistedmode, gNB-assisted mode, or base station-assisted mode. In an autonomousmode, the wireless device may select sidelink resources based onmeasurements within one or more resource pools (for example,pre-configure or network-assigned resource pools), sidelink resourceselections made by other wireless devices, and/or sidelink resourceusage of other wireless devices.

To select sidelink resources, a wireless device may observe a sensingwindow and a selection window. During the sensing window, the wirelessdevice may observe SCI transmitted by other wireless devices using thesidelink resource pool. The SCIs may identify resources that may be usedand/or reserved for sidelink transmissions. Based on the resourcesidentified in the SCIs, the wireless device may select resources withinthe selection window (for example, resource that are different from theresources identified in the SCIs). The wireless device may transmitusing the selected sidelink resources.

FIG. 18 illustrates an example of a resource pool for sidelinkoperations. A wireless device may operate using one or more sidelinkcells. A sidelink cell may include one or more resource pools. Eachresource pool may be configured to operate in accordance with aparticular mode (for example, assisted or autonomous). The resource poolmay be divided into resource units. In the frequency domain, eachresource unit may comprise, for example, one or more resource blockswhich may be referred to as a sub-channel. In the time domain, eachresource unit may comprise, for example, one or more slots, one or moresubframes, and/or one or more OFDM symbols. The resource pool may becontinuous or non-continuous in the frequency domain and/or the timedomain (for example, comprising contiguous resource units ornon-contiguous resource units). The resource pool may be divided intorepeating resource pool portions. The resource pool may be shared amongone or more wireless devices. Each wireless device may attempt totransmit using different resource units, for example, to avoidcollisions.

Sidelink resource pools may be arranged in any suitable manner. In thefigure, the example resource pool is non-contiguous in the time domainand confined to a single sidelink BWP. In the example resource pool,frequency resources are divided into a Nf resource units per unit oftime, numbered from zero to Nf−1. The example resource pool may comprisea plurality of portions (non-contiguous in this example) that repeatevery k units of time. In the figure, time resources are numbered as n,n+1 . . . n+k, n+k+1 . . . , etc.

A wireless device may select for transmission one or more resource unitsfrom the resource pool. In the example resource pool, the wirelessdevice selects resource unit (n,0) for sidelink transmission. Thewireless device may further select periodic resource units in laterportions of the resource pool, for example, resource unit (n+k,0),resource unit (n+2k,0), resource unit (n+3k,0), etc. The selection maybe based on, for example, a determination that a transmission usingresource unit (n,0) will not (or is not likely) to collide with asidelink transmission of a wireless device that shares the sidelinkresource pool. The determination may be based on, for example, behaviorof other wireless devices that share the resource pool. For example, ifno sidelink transmissions are detected in resource unit (n−k,0), thenthe wireless device may select resource unit (n,0), resource (n+k,0),etc. For example, if a sidelink transmission from another wirelessdevice is detected in resource unit (n−k,1), then the wireless devicemay avoid selection of resource unit (n,1), resource (n+k,1), etc.

Different sidelink physical channels may use different resource pools.For example, PSCCH may use a first resource pool and PSSCH may use asecond resource pool. Different resource priorities may be associatedwith different resource pools. For example, data associated with a firstQoS, service, priority, and/or other characteristic may use a firstresource pool and data associated with a second QoS, service, priority,and/or other characteristic may use a second resource pool. For example,a network (e.g., a base station) may configure a priority level for eachresource pool, a service to be supported for each resource pool, etc.For example, a network (e.g., a base station) may configure a firstresource pool for use by unicast UEs, a second resource pool for use bygroupcast UEs, etc. For example, a network (e.g., a base station) mayconfigure a first resource pool for transmission of sidelink data, asecond resource pool for transmission of discovery messages, etc.

FIG. 19A and FIG. 19B illustrate examples of a sidelink transmission. Inan example, a sidelink transmission may be transmitted via a sidelinkslot in the time domain. In an example, a wireless device may have datato transmit via sidelink. The wireless device may segment the data intoone or more transport blocks (TBs). The one or more TBs may comprisedifferent pieces of the data. A TB of the one or more TBs may be a datapacket of the data. The wireless device may transmit a TB of the one ormore TBs (e.g., a data packet) via one or more sidelink transmissions(e.g., via one or more sidelink slots). In an example, a sidelinktransmission (e.g., via a sidelink slot) may comprise SCI. The sidelinktransmission may further comprise a first TB. The SCI may comprise a1^(st)-stage SCI and a 2^(nd)-stage SCI. A PSCCH of the sidelinktransmission may carry the 1^(st)-stage SCI for transporting sidelinkscheduling information. A PSSCH of the sidelink transmission may carrythe 2^(nd)-stage SCI. The PSSCH of the sidelink transmission may furthercarry the first TB. In an example, the sidelink transmission may furthercomprise a guard time (GT in FIG. 19B) and a PSFCH. One or more HARQfeedbacks (e.g., ACK and/or NACK) may be transmitted via the PSFCH. Inan example, the PSCCH, the PSSCH, and the PSFCH may have differentnumber of subchannels (e.g., a different number of frequency resources)in the frequency domain.

The 1^(st)-stage SCI may be a SCI format 1-A. The SCI format 1-A maycomprise a plurality of fields used for scheduling of the first TB onthe PSSCH and the 2^(nd)-stage SCI on the PSSCH. The followinginformation may be transmitted by means of the SCI format 1-A.

-   -   A priority of the sidelink transmission. For example, the        priority may be a physical layer (e.g., layer 1) priority of the        sidelink transmission. For example, the priority may be        determined based on logical channel priorities of the sidelink        transmission;    -   Frequency resource assignment of the PSSCH;    -   Time resource assignment of the PSSCH;    -   Resource reservation period for a second TB;    -   Demodulation reference signal (DMRS) pattern;    -   A format of the 2nd-stage SCI;    -   Beta_offset indicator;    -   Number of DMRS port;    -   Modulation and coding scheme of the PSSCH;    -   Additional MCS table indicator;    -   PSFCH overhead indication;    -   Reserved bits.

The 2^(nd)-stage SCI may be a SCI format 2-A. The SCI format 2-A may beused for the decoding of the PSSCH, with HARQ operation when HARQ-ACKinformation includes ACK or NACK, or when there is no feedback ofHARQ-ACK information. The SCI format 2-A may comprise a plurality offields indicating the following information.

-   -   HARQ process number;    -   New data indicator;    -   Redundancy version;    -   Source ID of a transmitter (e.g., a transmitting wireless        device) of the sidelink transmission;    -   Destination ID of a receiver (e.g., a receiving wireless device)        of the sidelink transmission;    -   HARQ feedback enabled/disabled indicator;    -   Cast type indicator indicating that the sidelink transmission is        a broadcast, a groupcast and/or a unicast;    -   CSI request.

The 2^(nd)-stage SCI may be a SCI format 2-B. The SCI format 2-B may beused for the decoding of the PSSCH, with HARQ operation when HARQ-ACKinformation includes only NACK, or when there is no feedback of HARQ-ACKinformation. The SCI format 2-B may comprise a plurality of fieldsindicating the following information.

-   -   HARQ process number;    -   New data indicator;    -   Redundancy version;    -   Source ID of a transmitter (e.g., a transmitting wireless        device) of the sidelink transmission;    -   Destination ID of a receiver (e.g., a receiving wireless device)        of the sidelink transmission;    -   HARQ feedback enabled/disabled indicator;    -   Zone ID indicating a zone in which a transmitter (e.g., a        transmitting wireless device) of the sidelink transmission is        geographic located;    -   Communication range requirement indicating a communication range        of the sidelink transmission.

FIG. 20 illustrates an example of resource indication for a first TB(e.g., a first data packet) and resource reservation for a second TB(e.g., a second data packet). SCI of an initial transmission (e.g., afirst transmission) and/or retransmission of the first TB may compriseone or more first parameters (e.g., Frequency resource assignment andTime resource assignment) indicating one or more first time andfrequency (T/F) resources for transmission and/or retransmission of thefirst TB. The SCI may further comprise one or more second parameters(e.g., Resource reservation period) indicating a reservation period ofone or more second T/F resources for initial transmission and/orretransmission of the second TB.

In an example, in response to triggering a resource selection procedure,a wireless device may select one or more first T/F resources for initialtransmission and/or retransmission of a first TB. As shown in FIG. 20 ,the wireless device may select three resources for transmitting thefirst TB. The wireless device may transmit an initial transmission(initial Tx of a first TB in FIG. 20 ) of the first TB via a firstresource of the three resources. The wireless device may transmit afirst retransmission (1^(st) re-Tx in FIG. 20 ) of the first TB via asecond resource of the three resources. The wireless device may transmita second retransmission (2^(nd) re-Tx in FIG. 20 ) of the first TB via athird resource of the three resources. A time duration between astarting time of the initial transmission of the first TB and the secondretransmission of the first TB may be smaller than or equal to 32sidelink slots (e.g., T≤32 slots in FIG. 20 ). A first SCI may associatewith the initial transmission of the first TB. The first SCI mayindicate a first T/F resource indication for the initial transmission ofthe first TB, the first retransmission of the first TB and the secondretransmission of the first TB. The first SCI may further indicate areservation period of resource reservation for a second TB. A second SCImay associate with the first retransmission of the first TB. The secondSCI may indicate a second T/F resource indication for the firstretransmission of the first TB and the second retransmission of thefirst TB. The second SCI may further indicate the reservation period ofresource reservation for the second TB. A third SCI may associate withthe second retransmission of the first TB. The third SCI may indicate athird T/F resource indication for the second retransmission of the firstTB. The third SCI may further indicate the reservation period ofresource reservation for the second TB.

FIG. 21 and FIG. 22 illustrate examples of configuration information forsidelink communication. In an example, a base station may transmit oneor more radio resource control (RRC) messages to a wireless device fordelivering the configuration information for the sidelink communication.The configuration information may comprise a field ofsl-UE-SelectedConfigRP. A parameter sl-ThresPSSCH-RSRP-List in the fieldmay indicate a list of 64 thresholds. In an example, a wireless devicemay receive first sidelink control information (SCI) indicating a firstpriority. The wireless device may have second SCI to be transmitted. Thesecond SCI may indicate a second priority. The wireless device mayselect a threshold from the list based on the first priority in thefirst SCI and the second priority in the second SCI. Referring to secondexclusion in FIG. 26 , the wireless device may exclude resources fromcandidate resource set based on the threshold. A parametersl-MaxNumPerReserve in the field may indicate a maximum number ofreserved PSCCH/PSSCH resources indicated in an SCI. A parametersl-MultiReserveResource in the field may indicate if it is allowed toreserve a sidelink resource for an initial transmission of a TB by anSCI associated with a different TB, based on sensing and resourceselection procedure. A parameter sl-ResourceReservePeriodList mayindicate a set of possible resource reservation periods (e.g.,SL-ResourceReservedPeriod) allowed in a resource pool. Up to 16 valuesmay be configured per resource pool. A parameter sl-RS-ForSensing mayindicate whether DMRS of PSCCH or PSSCH is used for layer 1 (e.g.,physical layer) RSRP measurement in sensing operation. A parametersl-Sensing Window may indicate a start of a sensing window. A parametersl-SelectionWindowList may indicate an end of a selection window inresource selection procedure for a TB with respect to priority indicatedin SCI. Value n1 may correspond to 1*2μ, value n5 corresponds to 5*2μ,and so on, where μ=0, 1, 2, 3 for subcarrier spacing (SCS) of 15, 30,60, and 120 kHz respectively. A parameter SL-SelectionWindowConfig mayindicate a mapping between a sidelink priority (e.g., sl-Priority) andthe end of the selection window (e.g., sl-SelectionWindow).

The configuration information may comprise a parametersl-PreemptionEnable indicating whether sidelink pre-emption is disabledor enabled in a resource pool. For example, a priority levelp_preemption may be configured if the sidelink pre-emption is enabled.For example, if the sidelink pre-emption is enabled but the p_preemptionis not configured, the sidelink pre-emption may be applicable to allpriority levels.

The configuration information may comprise a parametersl-TxPercentageList indicating a portion of candidate single-slot PSSCHresources over total resources. For example, value p20 may correspond to20%, and so on. A parameter SL-TxPercentageConfig may indicate a mappingbetween a sidelink priority (e.g., sl-Priority) and the portion ofcandidate single-slot PSSCH resources over total resources (e.g.,sl-TxPercentage).

FIG. 23 illustrates an example format of a MAC subheader for sidelinkshared channel (SL-SCH). The MAC subheader for SL-SCH may comprise sevenheader fields V/R/R/R/R/SCR/DST. The MAC subheader is octet aligned. Forexample, the V field may be a MAC protocol date units (PDU) formatversion number field indicating which version of the SL-SCH subheader isused. For example, the SRC field may carry 16 bits of a Source Layer-2identifier (ID) field set to a first identifier provided by upperlayers. For example, the DST field may carry 8 bits of the DestinationLayer-2 ID set to a second identifier provided by upper layers. In anexample, if the V field is set to “1”, the second identifier may be aunicast identifier. In an example, if the V field is set to “2”, thesecond identifier may be a groupcast identifier. In an example, if the Vfield is set to “3”, the second identifier may be a broadcastidentifier. For example, the R field may indicate reserved bit.

FIG. 24 illustrates an example time of a resource selection procedure. Awireless device may perform the resource selection procedure to selectresources for one or more sidelink transmissions. As shown in FIG. 24 ,a sensing window of the resource selection procedure may start at time(n−T0) (e.g., parameter sl-SensingWindow). The sensing window may end attime (n−T_(proc,0)). New data of the one or more sidelink transmissionsmay arrive at the wireless device at time (n−T_(proc,0)). The timeperiod T_(proc,0) may be a processing delay of the wireless device todetermine to trigger the resource selection procedure. The wirelessdevice may determine to trigger the resource selection procedure at timen to select the resources for the new data arrived at time(n−T_(proc,0)). The wireless device may complete the resource selectionprocedure at time (n+T1). The wireless device may determine theparameter T1 based on a capability of the wireless device. Thecapability of the wireless device may be a processing delay of aprocessor of the wireless device. A selection window of the resourceselection procedure may start at time (n+T1). The selection window mayend at time (n+T2) indicating the ending of the selection window. Thewireless device may determine the parameter T2 based on a parameterT2min (e.g., sl-SelectionWindow). In an example, the wireless device maydetermine the parameter T2 subject to T2min≤T2≤PDB, where the PDB(packet delay budget) may be the maximum allowable delay (e.g., a delaybudget) for successfully transmitting the new data via the one or moresidelink transmissions. The wireless device may determine the parameterT2min to a corresponding value for a priority of the one or moresidelink transmissions (e.g., based on a parameterSL-SelectionWindowConfig indicating a mapping between a sidelinkpriority sl-Priority and the end of the selection windowsl-SelectionWindow). In an example, the wireless device may set theparameter T2=PDB if the parameter T2min>PDB.

FIG. 25 illustrates an example timing of a resource selection procedure.A wireless device may perform the resource selection procedure forselecting resources for one or more sidelink transmissions. Referring toFIG. 24 , a sensing window of initial selection may start at time(n−TO). The sensing window of initial selection may end at time(n−T_(proc,0)). New data of the one or more sidelink transmissions mayarrive at the wireless device at the time (n−T_(proc,0)). The timeperiod T_(proc,0) may be a processing delay for the wireless device todetermine to trigger the initial selection of the resources. Thewireless device may determine to trigger the initial selection at time nfor selecting the resources for the new data arrived at the time(n−T_(proc,0)). The wireless device may complete the resource selectionprocedure at time (n+T1). The time (n+T_(proc,1)) may be the maximumallowable processing latency for completing the resource selectionprocedure being triggered at the time n, where 0<T1≤T_(proc,1). Aselection window of initial selection may start at time (n+T1). Theselection window of initial selection may end at time (n+T2). Theparameter T2 may be configured, preconfigured, or determined at thewireless device.

The wireless device may determine first resources (e.g., selectedresources after resource selection with collision in FIG. 25 ) for theone or more sidelink transmissions based on the completion of theresource selection procedure at the time (n+T1). The wireless device mayselect the first resources from candidate resources in the selectionwindow of initial selection based on measurements in the sensing windowfor initial selection. The wireless device may determine a resourcecollision between the first resources and other resources reserved byanother wireless device. The wireless device may determine to drop thefirst resources for avoiding interference. The wireless device maytrigger a resource reselection procedure (e.g., a second resourceselection procedure) at time (m−T3) and/or before time (m−T3). The timeperiod T3 may be a processing delay for the wireless device to completethe resource reselection procedure (e.g., a second resource selectionprocedure). The wireless device may determine second resources (e.g.,reselected resource after resource reselection in FIG. 25 ) via theresource reselection procedure (e.g., a second resource selectionprocedure). The start time of the second resources may be time m.

In an example, at least one of time parameters TO, T_(proc,0),T_(proc,1), T2, and PDB may be configured by a base station to thewireless device. In an example, the at least one of the time parametersTO, T_(proc,0), T_(proc,1), T2, and PDB may be preconfigured to thewireless device. The at least one of the time parameters TO, T_(proc,0),T_(proc,1), T2, and PDB may be stored in a memory of the wirelessdevice. In an example, the memory may be a Subscriber Identity Module(SIM) card. In an example of FIG. 24 and FIG. 25 , the time n, m, TO,T1, T_(proc,0), T_(proc,1), T2, T2min, T3, and PDB may be in terms ofslots and/or slot index.

FIG. 26 illustrates an example flowchart of a resource selectionprocedure by a wireless device for transmitting a TB (e.g., a datapacket) via sidelink.

FIG. 27 illustrates an example diagram of the resource selectionprocedure among layers of the wireless device.

Referring to FIG. 26 and FIG. 27 , the wireless device may transmit oneor more sidelink transmissions (e.g., a first transmission of the TB andone or more retransmissions of the TB) for the transmitting of the TB.Referring to FIG. 19A and FIG. 19B, a sidelink transmission of the oneor more sidelink transmission may comprise a PSCCH. The sidelinktransmission may comprise a PSSCH. The sidelink transmission maycomprise a PSFCH. The wireless device may trigger the resource selectionprocedure for the transmitting of the TB. The resource selectionprocedure may comprise two actions. The first action of the two actionsmay be a resource evaluation action. Physical layer (e.g., layer 1) ofthe wireless device may perform the first action. The physical layer maydetermine a subset of resources based on the first action and report thesubset of resources to higher layer (e.g., RRC layer and/or MAC layer)of the wireless device. The second action of the two actions may be aresource selection action. The higher layer (e.g., RRC layer and/or MAClayer) of the wireless device may perform the second action based on thereported the subset of resources from the physical layer.

In an example, higher layer (e.g., RRC layer and/or MAC layer) of awireless device may trigger a resource selection procedure forrequesting the wireless device to determine a subset of resources. Thehigher layer may select resources from the subset of resources for PSSCHand/or PSCCH transmission. To trigger the resource selection procedure,e.g., in slot n, the higher layer may provide the following parametersfor the PSSCH and/or PSCCH transmission:

-   -   a resource pool, from which the wireless device may determine        the subset of resources;    -   layer 1 priority, prio_(TX) (e.g., sl-Priority referring to FIG.        21 and FIG. 22 ), of the PSSCH/PSCCH transmission;    -   remaining packet delay budget (PDB) of the PSSCH and/or PSCCH        transmission;    -   a number of sub-channels, L_(subCH), for the PSSCH and/or PSCCH        transmission in a slot;    -   a resource reservation interval, P_(rsvp_TX), in units of        millisecond (ms).

In an example, if the higher layer requests the wireless device todetermine a subset of resources from which the higher layer will selectthe resources for the PSSCH and/or PSCCH transmission for re-evaluationand/or pre-emption, the higher layer may provide a set of resources (r₀,r₁, r₂, . . . ) which may be subject to the re-evaluation and a set ofresources (r₀, r₁, r₂, . . . ) which may be subject to the pre-emption.

In an example, a base station (e.g., network) may transmit a messagecomprising one or more parameters to the wireless device for performingthe resource selection procedure. The message may be an RRC/SIB message,a MAC CE, and/or a DCI. In an example, a second wireless device maytransmit a message comprising one or more parameters to the wirelessdevice for performing the resource selection procedure. The message maybe an RRC message, a MAC CE, and/or a SCI. The one or more parametersmay indicate following information.

-   -   t2min_SelectionWindow (e.g., sl-SelectionWindow referring to        FIG. 21 and FIG. 22 ): an internal parameter T2min (e.g., T2min        referring to FIG. 24 ) may be set to a corresponding value from        the parameter t2min_SelectionWindow for a given value of        prio_(TX) (e.g., based on SL-SelectionWindowConfig referring to        FIG. 21 and FIG. 22 ).    -   SL-ThresRSRP_pi_pj (e.g., sl-ThresPSSCH-RSRP-List referring to        FIG. 21 and FIG. 22 ): a parameter may indicate an RSRP        threshold for each combination (p_(i), p_(j)), where p_(i) is a        value of a priority field in a received SCI format 1-A and p_(j)        is a priority of a sidelink transmission (e.g., the PSSCH/PSCCH        transmission) of the wireless device; In an example of the        resource selection procedure, an invocation of p_(j) may be        p_(j)=prio_(TX).    -   RSforSensing (e.g., sl-RS-ForSensing referring to FIG. 21 and        FIG. 22 ): a parameter may indicate whether DMRS of a PSCCH or a        PSSCH is used, by the wireless device, for layer 1 (e.g.,        physical layer) RSRP measurement in sensing operation.    -   sl-ResourceReservePeriodList (e.g., sl-ResourceReservePeriodList        referring to FIG. 21 and FIG. 22 )    -   t0_SensingWindow (e.g., sl-SensingWindow referring to FIG. 21        and FIG. 22 s ): an internal parameter T₀ may be defined as a        number of slots corresponding to t0_SensingWindow ms.    -   sl-xPercentage (e.g., based on SL-TxPercentageConfig referring        to FIG. 21 and FIG. 22 ): an internal parameter X (e.g.,        sl-TxPercentage referring to FIG. 21 and FIG. 22 ) for a given        prio_(TX) (e.g., sl-Priority referring to FIG. 21 and FIG. 22 )        may be defined as sl-xPercentage(prio_(TX)) converted from        percentage to ratio.    -   p_preemption (e.g., p_preemption referring to FIG. 21 and FIG.        22 ): an internal parameter prio_(pre) may be set to a higher        layer provided parameter p_preemption.

The resource reservation interval, P_(rsvp_TX), if provided, may beconverted from units of ms to units of logical slots, resulting inP′_(rsvp_TX).

Notation: (t₀ ^(SL), t₁ ^(SL), t₂ ^(SL), . . . ) may denote a set ofslots of a sidelink resource.

In the resource evaluation action (e.g., the first action in FIG. 26 ),the wireless device may determine a sensing window (e.g., the sensingwindow shown in FIG. 24 and FIG. 25 based on t0_SensingWindow) based onthe triggering the resource selection procedure. The wireless device maydetermine a selection window (e.g., the selection window shown in FIG.24 and FIG. 25 based on t2min_SelectionWindow) based on the triggeringthe resource selection procedure. The wireless device may determine oneor more reservation periods (e.g., parametersl-ResourceReservePeriodList) for resource reservation. In an example, acandidate single-slot resource for transmission R_(x,y) may be definedas a set of L_(subCH) contiguous sub-channels with sub-channel x+j inslot t_(y) ^(SL) where j=0, . . . , L_(subCH)−1. The wireless device mayassume that a set of L_(subCH) contiguous sub-channels in the resourcepool within a time interval [n+T₁, n+T₂] correspond to one candidatesingle-slot resource (e.g., referring to FIG. 24 and FIG. 25 ). A totalnumber of candidate single-slot resources may be denoted by M_(total).In an example, referring to FIG. 24 and FIG. 25 , the sensing window maybe defined by a number of slots in a time duration of [n−T₀,n−T_(proc,0)). The wireless device may monitor a first subset of theslots, of a sidelink resource pool, within the sensing window. Thewireless device may not monitor a second subset of the slots than thefirst subset of the slots due to half duplex. The wireless device mayperform the following actions based on PSCCH decoded and RSRP measuredin the first subset of the slots. In an example, an internal parameterTh(p_(i)) may be set to the corresponding value from the parameterSL-ThresRSRP_pi_pj for p_(j) equal to the value of prio_(TX) and thepriority value p_(i).

Referring to FIG. 26 and FIG. 27 , in the resource evaluation action(e.g., the first action in FIG. 26 ), the wireless device may initializea candidate resource set (e.g., a set S_(A)) to be a set of candidateresources. In an example, the candidate resource set may be the union ofcandidate resources within the selection window. In an example, acandidate resource may be a candidate single-subframe resource. In anexample, a candidate resource may be a candidate single-slot resource.In an example, the set S_(A) may be initialized to a set of allcandidate single-slot resources.

Referring to FIG. 26 and FIG. 27 , in the resource evaluation action(e.g., the first action in FIG. 26 ), the wireless device may perform afirst exclusion for excluding second resources from the candidateresource set based on first resources and one or more reservationperiods. In an example, the wireless device may not monitor the firstresources within a sensing window. In an example, the one or morereservation periods may be configured/associated with a resource pool ofthe second resources. In an example, the wireless device may determinethe second resources within a selection window which might be reservedby a transmission transmitted via the first resources based on the oneor more reservation periods. In an example, the wireless device mayexclude a candidate single-slot resource R_(x,y) from the set S_(A)based on following conditions:

-   -   the wireless device has not monitored slot t_(m) ^(SL) in the        sensing window.    -   for any periodicity value allowed by the parameter        sl-ResourceReservePeriodList and a hypothetical SCI format 1-A        received in the slot t_(m) ^(SL) with “Resource reservation        period” field set to that periodicity value and indicating all        subchannels of the resource pool in this slot, condition c of a        second exclusion would be met.

Referring to FIG. 26 and FIG. 27 , in the resource evaluation action(e.g., the first action in FIG. 26 ), the wireless device may perform asecond exclusion for excluding third resources from the candidateresource set. In an example, a SCI may indicate a resource reservationof the third resources. The SCI may further indicate a priority value(e.g., indicated by a higher layer parameter sl-Priority). The wirelessdevice may exclude the third resources from the candidate resource setbased on a reference signal received power (RSRP) of the third resourcesbeing higher than an RSRP threshold (e.g., indicated by a higher layerparameter sl-ThresPSSCH-RSRP-List). The RSRP threshold may be related tothe priority value based on a mapping list of RSRP thresholds topriority values configured and/or pre-configured to the wireless device.In an example, a base station may transmit a message to the wirelessdevice for configuring the mapping list. The message may be a radioresource control (RRC) message. In an example, the mapping list may bepre-configured to the wireless device. A memory of the wireless devicemay store the mapping list. In an example, a priority indicated by thepriority value may be a layer 1 priority (e.g., physical layerpriority). In an example, a bigger priority value may indicate a higherpriority of a sidelink transmission. A smaller priority value mayindicate a lower priority of the sidelink transmission. In anotherexample, a bigger priority value may indicate a lower priority of asidelink transmission. A smaller priority value may indicate a higherpriority of the sidelink transmission. In an example, the wirelessdevice may exclude a candidate single-slot resource R_(x,y) from the setS_(A) based on following conditions:

-   -   a) the wireless device receives an SCI format 1-A in slot t_(m)        ^(SL), and “Resource reservation period” field, if present, and        “Priority” field in the received SCI format 1-A indicate the        values P_(rsvp_RX) and prio_(RX);    -   b) the RSRP measurement performed, for the received SCI format        1-A, is higher than Th(prio_(RX));    -   c) the SCI format received in slot t_(m) ^(SL) or the same SCI        format which, if and only if the “Resource reservation period”        field is present in the received SCI format 1-A, is assumed to        be received in slot(s) t_(m+q×P′rsvp_RX) ^(SL) determines the        set of resource blocks and slots which overlaps with        R_(x,y+j×P′rsvp_TX) for q=1, 2, . . . , Q and j=0, 1, . . . ,        C_(resel)−1. Here, P′_(rsvp_RX) is P_(rsvp_RX) converted to        units of logical slots, Q=

$\left\lceil \frac{T_{scal}}{P_{{rsvp}\_{RX}}} \right\rceil$

-   -    if T_(rsvp_RX)<T_(scal) and n′−m≤P′_(rsvp_RX), where t_(n′)        ^(SL)=n if slot n belongs to the set (t₀ ^(SL), t₁ ^(SL), . . .        , t_(Tmax) ^(SL)), otherwise slot t_(n′) ^(SL) is the first slot        after slot n belonging to the set (t₀ ^(SL), t₁ ^(SL), . . . ,        t_(Tmax) ^(SL)); otherwise Q=1. T_(scal) is set to selection        window size T2 converted to units of ms.

Referring to FIG. 26 and FIG. 27 , in the resource evaluation action(e.g., the first action in FIG. 26 ), the wireless device may determinewhether remaining candidate resources in the candidate resource set aresufficient for selecting resources for the one or more sidelinktransmissions of the TB based on a condition, after performing the firstexclusion and the second exclusion. In an example, the condition may bethe total amount of the remaining candidate resources in the candidateresource set being more than X percent (e.g., indicated by a higherlayer parameter sl-TxPercentageList) of the candidate resources in thecandidate resource set before performing the first exclusion and thesecond exclusion. If the condition is not met, the wireless device mayincrease the RSRP threshold used to exclude the third resources with avalue Y and iteratively re-perform the initialization, first exclusion,and second exclusion until the condition being met. In an example, ifthe number of remaining candidate single-slot resources in the set S_(A)is smaller than X·M_(total), then Th(p_(i)) may be increased by 3 dB andthe procedure continues with re-performing of the initialization, firstexclusion, and second exclusion until the condition being met. In anexample, the wireless device may report the set S_(A) (e.g., theremaining candidate resources of the candidate resource set) to thehigher layer of the wireless device. In an example, the wireless devicemay report the set S_(A) (e.g., the remaining candidate resources of thecandidate resource set when the condition is met) to the higher layer ofthe wireless device, based on that the number of remaining candidatesingle-slot resources in the set S_(A) being greater than or equal toX·M_(total).

Referring to FIG. 26 and FIG. 27 , in the resource selection action(e.g., the second action in FIG. 26 ), the wireless device (e.g., thehigher layer of the wireless device) may select fourth resources fromthe remaining candidate resources of the candidate resource set (e.g.,the set S_(A) reported by the physical layer) for the one or moresidelink transmissions of the TB. In an example, the wireless device mayrandomly select the fourth resources from the remaining candidateresources of the candidate resource set.

Referring to FIG. 26 and FIG. 27 , in an example, if a resource r_(i)from the set (r₀, r₁, r₂, . . . ) is not a member of S_(A) (e.g., theremaining candidate resources of the candidate resource set when thecondition is met), the wireless device may report re-evaluation of theresource r_(i) to the higher layers.

Referring to FIG. 26 and FIG. 27 , in an example, if a resource r′_(i)from the set (r′₀, r′₁, r′₂, . . . ) is not a member of S_(A) (e.g., theremaining candidate resources of the candidate resource set when thecondition is met) due to exclusion in the second exclusion by comparisonwith the RSRP measurement for the received SCI format 1-A with anassociated priority prio_(RX), and satisfy one of the following twoconditions, then the wireless device may report pre-emption of theresource r′_(i) to the higher layers.

Condition 1: sl-PreemptionEnable is provided and is equal to ‘enabled’and prio_(TX)>prio_(RX)

Condition 2: sl-PreemptionEnable is provided and is not equal to‘enabled’, and prio_(RX)<prio_(pre) and prio_(TX)>prio_(RX)

In an example, if the resource r_(i) is indicated for re-evaluation bythe wireless device (e.g., the physical layer of the wireless device),the higher layer of the wireless device may remove the resource r_(i)from the set (r₀, r₁, r₂, . . . ). In an example, if the resource r′_(i)is indicated for pre-emption by the wireless device (e.g., the physicallayer of the wireless device), the higher layer of the wireless devicemay remove the resource r′_(i) from the set (r′₀, r′_(i), r′₂, . . . ).The higher layer of the wireless device may randomly select new time andfrequency resources from the remaining candidate resources of thecandidate resource set (e.g., the set S_(A) reported by the physicallayer) for the removed resources r_(i) and/or r′_(i). The higher layerof the wireless device may replace the removed resources r_(i) and/orr′_(i) by the new time and frequency resources. For example, thewireless device may remove the resources r_(i) and/or r′_(i) from theset (r₀, r₁, r₂, . . . ) and/or the set (r₀, r_(i), r₂, . . . ) and addthe new time and frequency resources to the set (r₀, r₁, r₂, . . . )and/or the set (r₀, r_(i), r₂, . . . ) based on the removing of theresources r_(i) and/or r′_(i).

Sidelink pre-emption may happen between a first wireless device and asecond wireless device. The first wireless device may select firstresources for a first sidelink transmission. The first sidelinktransmission may have a first priority. The second wireless device mayselect second resources for a second sidelink transmission. The secondsidelink transmission may have a second priority. The first resourcesmay partially and/or fully overlap with the second resources. The firstwireless device may determine a resource collision between the firstresources and the second resources based on that the first resources andthe second resources being partially and/or fully overlapped. Theresource collision may imply fully and/or partially overlapping betweenthe first resources and the second resources in time, frequency, code,power, and/or spatial domain. In an example, a bigger priority value mayindicate a lower priority of a sidelink transmission. A smaller priorityvalue may indicate a higher priority of the sidelink transmission. In anexample, the first wireless device may determine the sidelinkpre-emption based on the resource collision and the second prioritybeing higher than the first priority. That is, the first wireless devicemay determine the sidelink pre-emption based on the resource collisionand a value of the second priority being smaller than a value of thefirst priority. In another example, the first wireless device maydetermine the sidelink pre-emption based on the resource collision, thevalue of the second priority being smaller than a priority threshold,and the value of the second priority being smaller than the value of thefirst priority.

Referring to FIG. 25 , a first wireless device may trigger a firstresource selection procedure for selecting first resources (e.g.,selected resources after resource selection with collision in FIG. 25 )for a first sidelink transmission. A second wireless device may transmitan SCI indicating resource reservation of the first resource for asecond sidelink transmission. The first wireless device may determine aresource collision on the first resources between the first sidelinktransmission and the second sidelink transmission. The first wirelessdevice may trigger a resource re-evaluation (e.g., a resource evaluationaction of a second resource selection procedure) at and/or before time(m−T3) based on the resource collision. The first wireless device maytrigger a resource reselection (e.g., a resource selection action of thesecond resource selection procedure) for selecting second resources(e.g., reselected resources after resource reselection in FIG. 25 )based on the resource re-evaluation. The start time of the secondresources may be time m.

Referring to FIG. 26 , triggering of the resource reselection based onthe resource re-evaluation, at and/or before time (m−T3), may comprisefollowing actions:

-   -   Action 1: The first wireless device may initialize a candidate        resource set to be a set of candidate resources.    -   Action 2: The first wireless device may perform a first        exclusion.    -   Action 3: The first wireless device may perform a second        exclusion.    -   Action 4: If the first resources are still in the candidate        resource set after the first exclusion and the second exclusion,        a resource reselection of the first resources based on the        resource collision may not be triggered.    -   Action 5: If the first resources are not in the candidate        resource set after the first exclusion and the second exclusion        -   Action 5-1: In an example, if the first resources are            excluded in Action 3 and the SCI of the second resources            indicates a priority which can trigger pre-emption, a            resource reselection of the first resources based on the            resource collision may be triggered.        -   Action 5-2: In an example, if the first resources are            excluded in Action 3 and the SCI of the second resources            indicates a priority which cannot trigger pre-emption, the            resource reselection of the first resources based on the            resource collision may not be triggered.

In existing technologies, a first wireless device may select a first setof resources for one or more sidelink transmissions. The first wirelessdevice may trigger a first resource selection procedure, based onsensing results of channel environment at the first wireless device, forselecting the first set of resources. The first wireless device may nottake into account channel information at a desired receiver of the oneor more sidelink transmissions for the selecting of the first set ofresources. The desired receiver may have a hidden node problem and/or ahalf-duplex problem (i.e., unable to receive while transmitting and totransmit while receiving) when receiving the one or more sidelinktransmissions via the first set of resources. An inter-UE coordinationbetween the first wireless device and a second wireless device mayreduce the hidden node problem and/or the half-duplex problem at thedesired receiver. The second wireless device may be a coordinatingwireless device of the first wireless device. The first wireless devicemay send, to the second wireless device, a request message of theinter-UE coordination. The second wireless device may perform, based onthe request message, a second resource selection procedure for selectinga second set of resources for the one or more sidelink transmissions ofthe first wireless device. The second set of resources may comprisepreferred resources and/or non-preferred resources of the desiredreceiver. The second wireless device may send, to the first wirelessdevice, a coordination/assistance information comprising the second setof resources. The first wireless device may update the first set ofresources based on the coordination/assistance information for reducingthe hidden node problem and/or the half-duplex problem at the desiredreceiver.

Implementing the existing technologies for performing the inter-UEcoordination may increase signaling overhead and channel occupancy ofsidelink for transmitting/receiving the request message and thecoordination/assistance information. For example, the request messagemay comprise configuration parameters (e.g., referring to FIG. 26 andFIG. 27 ) of the first wireless device for performing the secondresource selection procedure at the second wireless device. Implementingthe existing technologies for performing the inter-UE coordination maynot reduce the hidden node problem and/or the half-duplex problem at thedesired receiver. For example, the second wireless device may determinethe second set of resources based on configuration parameters of thesecond wireless device. For example, a selection window of the secondresource selection by the second wireless device may be different from aselection window of the first resource selection by the first wirelessdevice. The second set of resources, thus, may not overlap with a timeduration of the first set of resources. The first wireless device maynot be able to update the first set of resources based on the second setof resources, because that using of the second set of resources may notmeet a PDB requirement of the one or more sidelink transmissions.

Embodiments of the present disclosure enables the first wireless deviceto indicate a slot in the request message. In an example, the slot maybe a slot n for triggering of the first resource selection procedure atthe first wireless device. In an example, the slot may be a slot (n+T1).In an example, the slot may be a slot of a first sidelink transmissionof the one or more sidelink transmissions. The second wireless devicemay determine a start time of a time duration for the selecting of thesecond set of resources (e.g., selection window of the second resourceselection) based on an index of the slot (e.g., the index of the slotmay indicate a time of the slot). In an example, the start time may bethe slot (n+T1). In an example, the start time may be a slot (n+T1′),where 0<T1′≤T_(proc,1) is up to the second wireless device. In anexample, the start time may be a slot (n+T_(proc,1)) indicating themaximum allowable processing latency for completing a resource selectionprocedure being triggered at the time n. In an example, the start timemay be the slot of the first sidelink transmission of the one or moresidelink transmissions. In an example, the request message may indicatea priority value and/or a PDB of the one or more sidelink transmissions.The second wireless device may determine an end time of the timeduration based on the priority value and/or the PDB. In an example, theend time may be a slot (n+T2). In an example, the end time may be a slot(n+T2′), where T2min≤T2′≤PDB is up to the second wireless device. In anexample, the end time may be a slot (n+T2min). In an example, the endtime may be a slot (n+PDB). In an example, the end time may be a slot ofa second sidelink transmission of the one or more sidelinktransmissions. For example, the second sidelink transmission may be alast sidelink transmissions of the one or more sidelink transmissions.In an example, the second wireless device may determine the slot is aslot in future. The second wireless device may send thecoordination/assistance information comprising the second set ofresources before the slot. In an example, the second wireless device maydetermine the slot is a slot in past. The second wireless device maydetermine the time duration based on the slot and one or morereservation periods of the one or more sidelink transmissions. The firstwireless device may determine a third set of resources based on thefirst set of resources and the second set of resources for one or moresecond sidelink transmissions. The one or more sidelink transmissionsmay indicate resource reservation for the one or more second sidelinktransmissions based on the one or more reservation periods.

Implementing the embodiments of the present disclosure may reducesignaling overhead and channel occupancy of sidelink for the inter-UEcoordination. Implementing the embodiments of the present disclosure mayalign a first time duration of the first set of resources and a secondtime duration of the second set of resources. Correspondingly, powerconsumption, processing latency, transmission delay, computationalcomplexity and/or hardware complexity for performing the inter-UEcoordination may be reduced for a wireless device.

FIG. 28 illustrates an example of inter-UE coordination for a sidelinktransmission. A first wireless device may be a transmitter of a sidelinktransmission. A second wireless device may be a desired receiver of thesidelink transmission. A third wireless device may not be a transmitterand/or a desired receiver of the sidelink transmission. In response toreceiving the sidelink transmission, the second wireless device maytransmit a feedback of the sidelink transmission to the first wirelessdevice. In an example, the feedback may be a HARQ ACK/NACK. Beforetransmitting the sidelink transmission, the first wireless device mayperform a first resource selection procedure for selecting a first setof resources for the sidelink transmission. The second wireless deviceand/or the third wireless device may be a coordinating wireless devicefor the sidelink transmission. The second wireless device and/or thethird wireless device may perform a second resource selection procedurefor selecting a second set of resources for the sidelink transmission ofthe first wireless device. The second wireless device and/or the thirdwireless device may send a message indicating the second set ofresources to the first wireless device. In an example, the second set ofresources may arrive at the first wireless device before the sidelinktransmission. The first wireless device may use the second set ofresources during the first resource selection procedure. For example,the first wireless device may select the first set of resources based onthe second set of resources. In an example, the second set of resourcesmay arrive at the first wireless device after the sidelink transmission.The first wireless device may perform a resource re-evaluation and/orre-selection based on the first set of resources and the second set ofresources. For example, the first wireless device may exclude one ormore resources of the second set of resources from the first set ofresources, if the second set of resources comprise non-preferredresources of the desired receiver. For example, the first wirelessdevice may replace one or more first resources of the first set ofresources with one or more second resources of the second set ofresources, if the second set of resources comprise preferred resourcesof the desired receiver. In an example, when the third wireless deviceis the coordinating wireless device, the third wireless device mayperform the second resource selection procedure taking into account thesidelink transmission and/or the feedback of the sidelink transmission.

FIG. 29 illustrates an example diagram of an inter-UE coordinationprocedure. A first wireless device may be a transmitter of one or moresidelink transmissions. A second wireless device may be a coordinatingwireless device for the one or more sidelink transmissions of the firstwireless device. In an example, the second wireless device may be adesired receiver of the one or more sidelink transmissions. In anexample, the second wireless device may not be a desired receiver of theone or more sidelink transmissions.

The first wireless device may transmit a first message to the secondwireless device. The first message may be a request message fortriggering an inter-UE coordination between the first wireless deviceand the second wireless device. The first message may be an RRC/SIB, aMAC CE, a DCI, and/or a SCI.

The first message may indicate a time (and/or a slot). The time may beindicated in terms of slot (e.g., an index of the slot). In an example,the first message may comprise a first field indicating the time (and/orthe slot). In an example, the first message may comprise an index of aslot for indicating the time (and/or the slot). In an example, the firstmessage may indicate the time (and/or the slot) based on a time offsetvalue. For example, the first wireless device may indicate the time(and/or the slot) based on a slot of transmitting the first message(e.g., an index of the slot) plus the time offset value. In an example,a base station and/or a third wireless device may send, to the firstwireless device and/or the second wireless device, an RRC/SIB, MAC CE,DCI, and/or SCI for configuring the time offset value. In an example,the time offset value may be pre-configured to the first wireless deviceand/or the second wireless device. A memory of the first wireless deviceand/or the second wireless device may store the time offset value. In anexample, the time (and/or the slot) may indicate a reference time forthe second wireless device to determine a time duration for selecting asecond set of resources. In an example, the first wireless device maytransmit the first message before the time (and/or the slot). In anexample, the first wireless device may transmit the first message afterthe time (and/or the slot). The first wireless device may transmit thefirst message via a sidelink transmission of the one or more sidelinktransmissions.

In response to receiving of the first message, the second wirelessdevice may determine, based on the time (and/or the slot), the timeduration for the selecting of the second set of resources. The secondwireless device may select the second set of resources during the timeduration (e.g., a selection window). In an example, the second wirelessdevice may trigger a second resource selection procedure for theselecting of the second set of resources. The time duration may be asecond selection window of the second resource selection procedure. Inan example, the second wireless device may not trigger a second resourceselection procedure for the selecting of the second set of resources.The second wireless device may select the second set of resources basedon a third set of resources (e.g., a previously selected set ofresources before the receiving of the first message) at the secondwireless device. In an example, the second wireless device may selectthe third set of resources for one or more second sidelink transmissionsby the second wireless device. In an example, the second wireless devicemay select the second set of resources based on the third set ofresources in response to a first resource size (e.g., L_(subCH)indicating a single slot in the time domain and a first number ofsubchannels in the frequency domain) of a resource of the first set ofresources being smaller than or equal to a second resource size (e.g., asingle slot in the time domain and a second number of subchannels in thefrequency domain) of a resource of the third set of resources. In anexample, the first message may indicate the first resource size (e.g.,L_(subCH)). In an example, the first message may comprise a second fieldindicating the first resource size (e.g., L_(subCH)).

The second wireless device may transmit, to the first wireless device, asecond message indicating the second set of resources. In an example,the second message may comprise a field indicating the second set ofresources. The field may comprise a bit map for indicating the secondset of resources. In an example, the second set of resources maycomprise preferred resource(s) and/or non-preferred resource(s) of adesired receiver of the one or more sidelink transmissions. In anexample, the second wireless device may be the desired receiver of theone or more sidelink transmissions. The second message may be an RRC, aMAC CE, and/or a SCI. In an example, the second wireless device maytransmit the second message before the time (and/or the slot) indicatedin the first message. In an example, the second wireless device maytransmit the second message after the time (and/or the slot) indicatedin the first message.

In an example, a preferred resource of the desired receiver may be aresource with a RSRP of the resources being lower than a RSRP threshold.In an example, a preferred resource of the desired receiver may be aresource with a priority value being greater than a priority threshold.In an example, a non-preferred resource of the desired receiver may be aresource with a RSRP being higher than the RSRP threshold. In anexample, a non-preferred resource of the desired receiver may be aresource with a priority value being smaller than the prioritythreshold. In an example, a base station and/or a third wireless devicemay send, to the desired receiver, an RRC/SIB, MAC CE, DCI, and/or SCIfor configuring the RSRP threshold and/or the priority threshold. In anexample, the RSRP threshold and/or the priority threshold may bepre-configured to the desired receiver. A memory of the desired receivermay store the time offset value. In an example, the priority thresholdmay be based on a priority threshold for triggering a sidelinkpre-emption (e.g., p_preemption referring to FIG. 21 and FIG. 22 ). Inan example, a bigger priority value may indicate a lower priority. Asmaller priority value may indicate a higher priority. For example, afirst sidelink transmission may have a first priority value. A secondsidelink transmission may have a second priority value. The firstpriority value may be greater than the second priority value, while afirst priority of the first sidelink transmission indicated by the firstpriority value is lower than a second priority of the second sidelinktransmission indicated by the second priority value.

In response to the receiving of the second message, the first wirelessdevice may select, based on the second set of resources, a first set ofresources for the one or more sidelink transmissions. In an example, thefirst wireless device may trigger a first resource selection procedurebased on the time (and/or the slot) indicated in the first message forselecting the first set of resources. Referring to FIG. 26 and FIG. 27 ,the first wireless device may determine, based on the second set ofresources, a candidate resource set of the first resource selectionprocedure in a first selection window of the first resource selectionprocedure. For example, the candidate resource set may comprise one ormore preferred resources of the second set of resources. For example,the candidate resource set may not comprise one or more non-preferredresources of the second set of resources. The first wireless device mayexclude the one or more non-preferred resources of the second set ofresources from the candidate resource set. In an example, the firstwireless device may exclude the one or more non-preferred resources ofthe second set of resources from the candidate resource set in aresource evaluation action of the first resource selection procedure. Inan example, the first wireless device may exclude the one or morenon-preferred resources of the second set of resources from thecandidate resource set in a resource selection action of the firstresource selection procedure. In an example, the first resourceselection procedure may be subject to an initial resource selection forthe one or more sidelink transmissions. In an example, the firstresource selection procedure may be subject to re-evaluation and/orpre-emption of resources for the one or more sidelink transmissions.

The first wireless device may transmit the one or more sidelinktransmissions based on the first set of resources and the second set ofresources.

FIG. 30 illustrates examples of indicating a time by a first wirelessdevice and an estimation of the time by a second wireless device.Referring to FIG. 29 , a first wireless device may be a transmitter ofone or more sidelink transmissions. A second wireless device may be acoordinating wireless device for the one or more sidelink transmissionsof the first wireless device. The first wireless device may transmit afirst message to the second wireless device indicating a time for thesecond wireless device. The second wireless device may determine a timeduration for selecting a second set of resources based on the time.

In an example, the time may be time n (e.g., a slot with an index n).The first wireless device may determine to select a first set ofresources at time n. The first wireless device may or may not trigger afirst resource selection procedure for selecting the first set ofresources at time n. Referring to FIG. 24 to FIG. 27 , the firstwireless device may determine a first selection window of the firstresource selection procedure. The first selection window may start fromtime (n+T1). Based on the time n, the second wireless device may or maynot trigger a second resource selection procedure for selecting thesecond set of resources. The time duration may be a second selectionwindow of the second resource selection procedure. The second wirelessdevice may determine that the time duration (e.g., the second selectionwindow) starts from time (n+T_(proc,1)).

In an example, the time may be time n. Based on the time n, the secondwireless device may determine that the time duration (e.g., the secondselection window) starts from time (n+T1′), where 0<T1′≤T_(proc,1) is upto implementation of the second wireless device.

In an example, the time may be time (n+T1). Based on the time (n+T1),the second wireless device may determine that the time duration (e.g.,the second selection window) starts from time (n+T1).

In an example, the time may be a time of a first sidelink transmissionof the one or more sidelink transmissions. Based on the time, the secondwireless device may determine that the time duration (e.g., the secondselection window) starts from the time (e.g., the time of the firstsidelink transmission of the one or more sidelink transmissions).

FIG. 31 illustrates examples of indicating a time by a first wirelessdevice and an estimation of the time by a second wireless device.Referring to FIG. 29 and FIG. 30 , a first wireless device may be atransmitter of one or more sidelink transmissions. A second wirelessdevice may be a coordinating wireless device for the one or moresidelink transmissions of the first wireless device. The first wirelessdevice may transmit a first message to the second wireless deviceindicating a time for the second wireless device. The second wirelessdevice may determine a time duration for selecting a second set ofresources based on the time.

In an example, the time may be time (n+T2). The first wireless devicemay determine to select a first set resources at time n. The firstwireless device may or may not trigger a first resource selectionprocedure for selecting the first set of resources at time n. Referringto FIG. 24 to FIG. 27 , the first wireless device may determine a firstselection window of the first resource selection procedure. The firstselection window may end at time (n+T2). Based on the time (n+T2), thesecond wireless device may or may not trigger a second resourceselection procedure for selection the second set of resources. The timeduration may be a second selection window of the second resourceselection procedure. The second wireless device may determine that thetime duration (e.g., the second selection window) ends at time (n+T2).

In an example, the time may be time n. The first message may indicate aPDB of the one or more sidelink transmissions. In an example, the firstmessage may comprise a field indicating the PDB. Based on the time n,the second wireless device may determine that the time duration (e.g.,the second selection window) ends at time (n+PDB).

In an example, the time may be time n. The first message may indicate apriority value of the one or more sidelink transmissions. In an example,the first message may comprise a field indicating the priority value.Based on the time n and the priority value, the second wireless devicemay determine that the time duration (e.g., the second selection window)ends at time (n+T2min) (e.g., referring to sl-SelectionWindowList inFIG. 21 and FIG. 22 ). In an example, the second wireless device maydetermine T2min based on an association mapping between T2min and thepriority value.

In an example, the time may be time n. The first message may indicate aPDB of the one or more sidelink transmissions and/or a priority value ofthe one or more sidelink transmissions. In an example, the first messagemay comprise a field indicating the PDB and/or the priority value of theone or more sidelink transmissions. Based on the time n, the secondwireless device may determine that the time duration (e.g., the secondselection window) ends at time (n+T2′), where T2min≤T2′≤PDB is up toimplementation of the second wireless device.

In an example, the time may be a time of a second sidelink transmissionof the one or more sidelink transmissions. The second sidelinktransmission may be the last sidelink transmission of the one or moresidelink transmissions. Based on the time, the second wireless devicemay determine that the time duration (e.g., the second selection window)ends at the time (e.g., the time of the second sidelink transmission ofthe one or more sidelink transmissions).

In an example of periodic sidelink transmissions, a first wirelessdevice may have a plurality of transport blocks (TBs) for a desiredwireless device. The first wireless device may transmit, to the desiredwireless device, one or more first sidelink transmissions of theperiodic sidelink transmissions before successfully delivering a firstTB of the plurality of TBs. The first wireless device may transmit, tothe desired wireless device, one or more second sidelink transmissionsof the periodic sidelink transmissions before successfully delivering asecond TB of the plurality of TBs. A second wireless device may be acoordinating wireless device of the periodic sidelink transmissions. Thesecond wireless device may determine that a time duration (e.g., asecond selection window of a second resource selection procedure of thesecond wireless device) ends at the last slot of the one or more firstsidelink transmissions based on receiving of the first TB. The secondwireless device may select a second set of resources based on the timeduration. The second wireless device may transmit a second messageindicating the second set of resources to the first wireless device. Inresponse to receiving the second message, the first wireless device mayselect, based on the second set of resources, a first set of resourcesfor the one or more second sidelink transmissions.

The second wireless device may update the end time of the time durationbased on receiving of the second TB. For example, the second wirelessdevice may determine (e.g., update the end time of the time duration)that the time duration (e.g., the second selection window) ends at thelast slot of the one or more second sidelink transmissions based onreceiving of the second TB. The second wireless device may select athird set of resources based on the time duration with updated end time.The second wireless device may transmit, to the first wireless device, athird message indicating the third set of resources. In response toreceiving the third message, the first wireless device may update, basedon the third set of resources, the first set of resources for one ormore third sidelink transmissions of the periodic sidelinktransmissions, and so for remaining sidelink transmissions of theperiodic sidelink transmissions.

In an example, referring to FIG. 29 to FIG. 31 , a first wireless devicemay be a transmitter of one or more sidelink transmissions. A secondwireless device may be a coordinating wireless device for the one ormore sidelink transmissions of the first wireless device. The firstwireless device may transmit a first message to the second wirelessdevice indicating a time for the second wireless device. The secondwireless device may determine a second time duration for selecting asecond set of resources based on the time. The second wireless devicemay transmit a second message indicating the second set of resources tothe first wireless device. The first wireless device may select, basedon the second set of resources, a first set of resources in a first timeduration. In an example, the first time duration may be a firstselection window of a first resource selection procedure (e.g.,triggered by the first wireless device) for the selecting of the firstset of resources. The second time duration may be a second selectionwindow of a second resource selection procedure (e.g., triggered by thesecond wireless device) for the selecting of the second set ofresources.

In an example, in order to make sure that the first time durationoverlaps with the second time duration, the second wireless device maydetermine the second time duration based on the time (e.g., indicated inthe first message) plus a time offset value. The time offset value maybe a number multiplied by a reservation period (e.g., the reservationperiod is a resource reservation interval, P_(rsvp_TX), in units ofmillisecond) of the one or more sidelink transmissions. In an example,the first message may indicate the reservation period. In an example, aSCI of the one or more sidelink transmissions may comprise the resourceperiod (e.g., Resource reservation period).

FIG. 32 illustrates an example of determining a reference time based onthe time indication in the first message and the time offset value. Inan example, the second wireless device may receive the first messageafter the time indicated in the first message. In an example, the timeindicated in the first message may be time n (e.g., a slot with an indexn). In an example, the second wireless device may determine the secondtime duration based on the time indicated in the first message plus atime offset, e.g., (n+m×P_(rsvp_TX)), where m is a number andP_(rsvp_TX) is a reservation period.

In an example, a first wireless device may receive, from a secondwireless device, a first message indicating a slot. The second wirelessdevice may select a second set of resources for one or more sidelinktransmissions based on a first set of resources and/or an index of theslot. The first wireless device may determine, based on the index of theslot, a start time of a time duration. The first wireless device mayselect the first set of resources during the time duration. The firstwireless device may transmit, to the second wireless device, a secondmessage indicating the first set of resources.

In an example, the index of the slot may indicate a time of triggering afirst resource selection procedure by the second wireless device for theone or more sidelink transmissions. In an example, the first wirelessdevice may determine, based on the index of the slot and a time offset,the start time of the time duration. In an example, the index of theslot may indicate a start time of a selection window in a first resourceselection procedure for the one or more sidelink transmissions. Thesecond wireless device may trigger the first resource selectionprocedure for the one or more sidelink transmissions. In an example, theindex of the slot may indicate a time of a first sidelink transmissionof the one or more sidelink transmissions.

In an example, the first wireless device may determine, based on theindex of the slot, an end time of the time duration. In an example, theone or more sidelink transmissions may have a priority value. In anexample, the first wireless device may determine the end time of thetime duration based on the priority value. In an example, the firstmessage may indicate the priority value. In an example, the firstmessage may indicate a PDB of the one or more sidelink transmissions. Inan example, the first wireless device may determine the end time of thetime duration based on the PDB. In an example, the first message mayindicate a PDB of the one or more sidelink transmissions. In an example,the first wireless device may determine the end time of the timeduration based on the PDB and the priority value. In an example, thefirst wireless device may determine, based on a time of a secondsidelink transmission of the one or more sidelink transmissions, an endtime of the time duration. In an example, the first message may indicatean end time of the time duration. In an example, the first message mayindicate a length of the time duration (in terms of slots).

In an example, a first wireless device may receive, from a secondwireless device, a first message indicating a slot. The first wirelessdevice may receive, from the second wireless device, one or moresidelink transmissions based on a set of resources and/or an index ofthe slot. The first wireless device may determine, based on the index ofthe slot, a start time of a time duration. The first wireless device mayselect the set of resources during the time duration. The first wirelessdevice may transmit, to the second wireless device, a second messageindicating the set of resources.

In an example, a first wireless device may receive, from a secondwireless device, a first message indicating a slot for a resourceselection procedure of the first wireless device and/or a priority valueof one or more sidelink transmissions of the second wireless device. Thefirst wireless device may trigger the resource selection procedure forselecting resources for the one or more sidelink transmissions. Thefirst wireless device may determine, based on an index of the slot, astart time of a selection window of the resource selection procedure.The first wireless device may determine, based on the priority value, anend time of the selection window. The first wireless device may selectthe resources in the selection window. The first wireless device maytransmit, to the second wireless device, a second message indicating theresources.

What is claimed is:
 1. A method comprising: receiving, by a firstwireless device from a second wireless device, a first medium accesscontrol (MAC) control element (CE) requesting for an inter-UEcoordination between the first wireless device and the second wirelessdevice, wherein the first MAC CE indicates a start time and an end timeof a selection window for a resource selection procedure of the secondwireless device to select resources for one or more sidelinktransmissions by the second wireless device; selecting, by the firstwireless device, a preferred resource set or a non-preferred resourceset during the selection window; transmitting, to the second wirelessdevice, a second MAC CE indicating the preferred resource set or thenon-preferred resource set for the second wireless device to selectresources for the one or more sidelink transmissions; and receiving, bythe first wireless device, the one or more sidelink transmissions. 2.The method of claim 1, wherein: the end time comprises a first referencetime, n+T2, of the selection window; a slot with a slot index nindicates a time for triggering a second resource selection procedure bythe second wireless device for the one or more sidelink transmissions;and T2 is determined by the second wireless device, based on T2≥T2min,wherein T2min is associated with a priority value of the one or moresidelink transmissions.
 3. The method of claim 2, wherein the firstreference time is based on a first slot index.
 4. The method of claim 1,wherein: the start time comprises a second reference time, n+T1, of theselection window; T1 is determined, by the second wireless device, basedon T1≤T_(proc,1); and T_(proc,1) is a maximum processing latency forcompleting the second resource selection procedure being triggered atthe slot index n for the one or more sidelink transmissions.
 5. Themethod of claim 4, wherein the second reference time is indicated by asecond slot index.
 6. The method of claim 1, further comprisingdetermining, by the first wireless device and based on the first MAC CE,the selection window.
 7. The method of claim 1, wherein the selecting ofthe preferred resource set or the non-preferred resource set during theselection window is based on a first resource selection procedure.
 8. Afirst wireless device comprising: one or more processors; and memorystoring instructions that, when executed by the one or more processors,cause the first wireless device to: receive, from a second wirelessdevice, a first medium access control (MAC) control element (CE)requesting for an inter-UE coordination between the first wirelessdevice and the second wireless device, wherein the first MAC CEindicates a start time and an end time of a selection window for aresource selection procedure of the second wireless device to selectresources for one or more sidelink transmissions by the second wirelessdevice; select a preferred resource set or a non-preferred resource setduring the selection window; transmit, to the second wireless device, asecond MAC CE indicating the preferred resource set or the non-preferredresource set for the second wireless device to select resources for theone or more sidelink transmissions; and receive the one or more sidelinktransmissions.
 9. The first wireless device of claim 8, wherein: the endtime comprises a first reference time, n+T2, of the selection window; aslot with a slot index n indicates a time for triggering a secondresource selection procedure by the second wireless device for the oneor more sidelink transmissions; and T2 is determined by the secondwireless device, based on T2≥T2min, wherein T2min is associated with apriority value of the one or more sidelink transmissions.
 10. The firstwireless device of claim 9, wherein the first reference time is based ona first slot index.
 11. The first wireless device of claim 8, wherein:the start time comprises a second reference time, n+T1, of the selectionwindow; T1 is determined, by the second wireless device, based onT1≤T_(proc,1); and T_(proc,1) is a maximum processing latency forcompleting the second resource selection procedure being triggered atthe slot index n for the one or more sidelink transmissions.
 12. Thefirst wireless device of claim 11, wherein the second reference time isindicated by a second slot index.
 13. The first wireless device of claim8, further comprising determining, by the first wireless device andbased on the first MAC CE, the selection window.
 14. The first wirelessdevice of claim 8, wherein the selecting of the preferred resource setor the non-preferred resource set during the selection window is basedon a first resource selection procedure.
 15. A non-transitory computerreadable medium comprising instructions that, when executed by aprocessor, cause a first wireless device to: receive, from a secondwireless device, a first medium access control (MAC) control element(CE) requesting for an inter-UE coordination between the first wirelessdevice and the second wireless device, wherein the first MAC CEindicates a start time and an end time of a selection window for aresource selection procedure of the second wireless device to selectresources for one or more sidelink transmissions by the second wirelessdevice; select a preferred resource set or a non-preferred resource setduring the selection window; transmit, to the second wireless device, asecond MAC CE indicating the preferred resource set or the non-preferredresource set for the second wireless device to select resources for theone or more sidelink transmissions; and receive the one or more sidelinktransmissions.
 16. The computer readable medium of claim 15, wherein:the end time comprises a first reference time, n+T2, of the selectionwindow; a slot with a slot index n indicates a time for triggering asecond resource selection procedure by the second wireless device forthe one or more sidelink transmissions; and T2 is determined by thesecond wireless device, based on T2≥T2min, wherein T2min is associatedwith a priority value of the one or more sidelink transmissions.
 17. Thecomputer readable medium of claim 16, wherein the first reference timeis based on a first slot index.
 18. The computer readable medium ofclaim 15, wherein: the start time comprises a second reference time,n+T1, of the selection window; T1 is determined, by the second wirelessdevice, based on T1≤T_(proc,1); and T_(proc,1) is a maximum processinglatency for completing the second resource selection procedure beingtriggered at the slot index n for the one or more sidelinktransmissions.
 19. The computer readable medium of claim 18, wherein thesecond reference time is indicated by a second slot index.
 20. Thecomputer readable medium of claim 15, further comprising determining, bythe first wireless device and based on the first MAC CE, the selectionwindow.